A bed-in-a-box is a mattress that ships compressed in a box to your front door. It’s an easy way to order a new bed, and cuts out the inconveniences of brick-and-mortar stores, and waiting for delivery people to drop your bed off in-person. They’re often excellent options for college students or anyone moving to a new city, as the bed gets shipped right to your doorstep and prevents a difficult setup.
The best bed-in-a-box for you is still going to depend on your specific sleep needs and preferences, like your sleeping position, body weight, preferred temperature, and whether or not you sleep with a partner or a pet. Because of this, we’ve done a full roundup of the best beds-in-a-box, and who they are (or aren’t) good for.
Our Top Bed-In-A-Box Pick
Nectar leads this list because it’s not only a bed-in-box (of course), but it’s also a high-quality memory foam mattress that exceeds our expectations. With excellent materials and a thoughtful construction, folks should get a nice balance of pressure relief and support.
The Best Bed-in-a-Box Mattresses
- Best Overall Mattress-in-a-Box – Nectar
- Best Mattress-in-a-Box for Couples – DreamCloud
- Best Mattress in-a-Box for Side Sleepers – Helix Midnight
- Best Mattress-in-a-Box for Combination Sleepers – Brooklyn Bedding Signature Hybrid
- Best Hybrid Mattress-in-a-Box – WinkBed
- Best Mattress-in-a-Box for Back Sleepers – Nolah Evolution
- Best Soft Mattress-in-a-Box – Bear Elite Hybrid
- Best Memory Foam Mattress-in-a-Box – Emma Original
- Best Mattress-in-a-Box for Heavy People – Titan Plus
- Best Organic Mattress-in-a-Box – Birch Natural
Best Mattress-In-A-Box 2024 Video Review
What We Look For In The Best Mattress In A Box
Shipping and Delivery
When looking for the best mattress in a box, we prioritize how easy the shipping and setup are. We are looking at how the bed will be delivered, what shape the box is, and how long it will take to ship. This can sometimes be a bit of a confusing or difficult process, so we made sure to simplify it for you. We checked out all of the details of shipping and delivery, and paid special attention to the convenience of each brand and what kind of delivery options they offer, for all of the mattresses on this list so you know exactly what to expect from your bed in a box.
Comfort and Support
Even though your mattress is being ordered online, you should still have the peace of mind of knowing that your bed will be comfortable and supportive. To help you ensure this, we used a pressure map to test the supportive capacity and pressure relieving technologies of each of the mattresses in this list. We also tried each one out ourselves to feel how comfortable and supportive they were in all sleeping positions. So, even though you cannot try the mattress before it arrives, you should have a sense of how comfortable it is.
Trial Period and Return Policy
As we mentioned, you often can’t try your boxed mattress until it arrives, which makes it all the more important that you can return the mattress if you don’t like it. Each of the mattresses on this list have great trial periods, return policies and warranties so you can be confident when making your next mattress purchase.
Compare the Best Mattresses in a Box
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| Nectar Mattress | DreamCloud Original Mattress | Helix Midnight Mattress | Brooklyn Bedding Signature Hybrid Mattress | WinkBed Mattress | Nolah Evolution Hybrid Mattress | Bear Elite Hybrid Mattress | Emma Mattress | Titan Plus | Birch Natural Mattress | |
| Rating | ||||||||||
| Firmness | Medium-firm: 6.5/10 | Firm: 7/10 | Medium-firm: 6.5/10 | Medium-firm: 6.5/10 | Firm: 7/10 | Multiple firmness options | Multiple firmness options | Firm: 7/10 | Firm: 7.5/10 | Firm: 7/10 |
| Material | Foam | Hybrid | Hybrid | Hybrid | Hybrid | Hybrid | Hybrid | Foam | Hybrid | Hybrid |
| Cooling | — | — | — | — | — | |||||
| Best For |
Back Sleepers, Back Pain, Stomach Sleepers, Side Sleepers, Couples
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Back Sleepers,
Hot Sleepers, Seniors |
Couples,
Back Sleepers, Side Sleepers |
Couples,
Back Sleepers, Hip Pain |
Back Sleepers, Stomach Sleepers, Back Pain, Hot Sleepers, Side Sleepers
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Side Sleepers, Back Sleepers, Hip Pain, Seniors,
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Back Sleepers, Stomach Sleepers, Hot Sleepers, Hip Pain, Seniors
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Hot Sleepers,
Kids, Back Sleepers |
Back Sleepers, Stomach Sleepers, Back Pain, Hip Pain, Seniors
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Back Sleepers, Stomach Sleepers, Hot Sleepers, Seniors,
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Nectar – Best Overall Mattress-in-a-Box
The Nectar Classic is a memory foam mattress that provides solid support for most light to average weight sleepers. The cushioning memory foam allows for plenty of pain relief around the lower lumbar spine. Most back sleepers and side sleepers should enjoy the pressure relief. Plus, a lengthy trial period, lifetime warranty, and affordable price make the Nectar a reassuring choice for many. Watch our video review to learn more.
What our tester says:
“I think memory foam lovers should be happy on the Nectar. This bed has a classic memory foam feel, so there’s lots of sinkage, contouring, and pressure relief. This can be great for anyone with shoulder pain or hip pain since it gives them cushioning at sensitive pressure points.” – Nichole Mondshein, lead reviewer and staff writer
Expert Opinion
Those looking for a bed-in-a-box that’s fitting for a wide variety of sleepers should turn to the original Nectar mattress. The Nectar is a memory foam mattress that has a simple yet effective construction, with a therapeutic comfort layer and a breathable cover that helps cool down hot sleepers. This layer, along with its transition foam layer, allow the sleeper lots of cushioning without having them sink too far into the material. This makes it a phenomenal option for folks with back pain.
The Nectar scored a 6.5 out of 10 on our firmness scale, making the Nectar the industry standard of 6.5 for a medium-firm mattress. That means it gives you some contouring while still offering lots of support with its layer of high-density support foam. Despite the all-foam construction, the Nectar shouldn’t be prone to sagging.
What Our Tester Says
How was delivery and setup?
Delivery was speedy, with Nectar delivering the mattress right to our mattress lab. It was also a fairly light mattress to unbox, due to its all-foam construction. However, like with many bed-in-a-box mattresses, there was a slight off-gassing period. This is nothing to worry about; the odor dissipated after 24 hours and the Nectar was ready to use.
How would you describe the firmness and feel of the mattress?
I found the Nectar’s foams to be very soft, cradling my body and allowing me to sink deeply into its layers. There’s a lot of pressure relief here, and I felt comfortable resting on both my side and my back.
Is there anything you would tell people to watch out for with this mattress?
I don’t think the Nectar is going to be firm enough for heavier stomach sleepers. They should check out or best mattress for stomach sleepers list, which features beds that are firm enough to keep the hips in line with the shoulders for a healthy spinal alignment.
Learn more in our full Nectar mattress review. You can also click here to get the best deal or take a look at our roundup of the best mattresses of 2024 for more options.
DreamCloud – Best Mattress-in-a-Box for Couples
With soft foam and a sturdy layer of innerspring coils, the DreamCloud strikes a balance between comfort and support — a little bit of contouring up top and on-top-of-the-bed feel that comes from the bottom. It’s a fairly firm mattress that we think is most comfortable for back sleepers. It also has some luxury touches such as a cashmere-blend cover that are reminiscent of a high-end hotel. Learn more in our DreamCloud video review.
What our tester says:
“I really like how luxurious this mattress feels and how it could work for a variety of sleepers. Along with that, I found that the breathable cashmere cover helps the DreamCloud sleep cool throughout the night. Thanks to its medium-firm to firm support, I think the DreamCloud is a durable mattress. It balances support with plenty of pressure relief for back sleepers.” – Bridget Chapman, former Sleepopolis senior product editor
Expert Opinion
When choosing a mattress, most couples are looking at four factors: motion transfer, sex, cooling, and edge support. Taking a look at the DreamCloud, it’s easy to see why we picked this mattress as our favorite bed-in-a-box. First off, the DreamCloud did well on our responsiveness test. We found it easy to move around on top of this bed, so it’s suitable for sex. The DreamCloud also excelled at cooling. It has cooling gel infusions in its comfort layer, as well as lots of room for airflow between the coils at the bottom. Our edge support test showed some impressive results as well, so partners should be able to make full use of the mattress surface.
The DreamCloud showed overall decent motion transfer results on our motion isolation test, which is conducted by dropping a 10-pound steel ball from three different heights and using a seismometer to see how much movement travels across the top of the mattress. Because it’s a hybrid, you might still feel larger movements, but smaller ones should be sufficiently trapped by the plush cover and comfort layer.
What Our Tester Says
How was delivery and setup?
Delivery was prompt and convenient, but I should note that, due to its extra layers and coils, the DreamCloud is heavier than a lot of other bed-in-a-box mattresses out there. I recommend asking someone to help you move it into your sleeping space and set it up. It does have handles on the side, so it gives you something to hold onto during transportation.
How would you describe the firmness and feel of the mattress?
I found the DreamCloud to be on the firmer side and give it a score of 7 out of 10 on the mattress firmness scale. It has more of a springy, on-top-of-the bed feel that I found worked best for back sleeping and combination sleeping. It’s very easy to move around and switch positions on this bed.
Is there anything you would tell people to watch out for with this mattress?
I think strict side sleepers might find that the DreamCloud sleeps a little too firm for their liking. These sleepers usually need a softer mattress that will provide extra pressure relief for their hips and shoulders. To find other options, they can take a look at our roundup of the best mattresses for side sleepers.
Learn more in our full DreamCloud mattress review. You can also click here to get the best deal, or take a look at our best mattresses for couples for other great mattress options.
Helix Midnight – Best Mattress-in-a-Box for Side Sleepers
The Helix Midnight is amongst Helix’s line of six standard mattresses. It’s known for its more balanced feel, allowing it to accommodate a wide range of sleepers. We also recommend it for couples, as it scored well on our motion isolation, responsiveness, edge support, and cooling tests. For a plusher and more cooling version of this mattress, see the Helix Midnight Luxe. Learn more in our video review.
What our tester says:
“I would recommend this mattress for side or back sleepers because it’s supportive, without putting pressure on your joints.” – Nichole Mondshein, lead reviewer and staff writer
Expert Opinion
Helix started off with an original line of six hybrid beds-in-a-box, each with a different level of firmness. The Midnight — in addition to being their most popular bed — was designed to be the medium-firm model, and that’s the exact score we gave it on the mattress firmness scale (a 6.5 out of 10). We think it’s an especially good fit for side sleepers, as its combination of plush memory foam and pocketed coils creates a good amount of cushioning at the shoulders and hips (where side sleepers put the most pressure) while still giving them enough of a lift to keep their spine neutrally aligned.
We also think the Midnight is a solid choice for hot sleepers. The coils in the construction create a ton of breathability, which allows air to flow through the mattress. Another bonus of the coils is that they give the bed some bounce, making it one of the best mattresses for sex and for combination sleepers to change positions.
What Our Tester Says
How was delivery and setup?
Helix delivered the Midnight on time, right to the doorstep of our mattress lab. Because it’s a bed-in-a-box mattress, you should be prepared for an off-gassing period that usually lasts 24 to 72 hours. You can speed up the process of the odor going away by placing the bed upright in a well-ventilated room.
How would you describe the firmness and feel of the mattress?
I experienced the Helix Midnight as medium firm, which is a 6.5 out of 10 on our mattress firmness scale. Back sleepers and side sleepers should both be comfortable, getting an optimal blend of comfort and support.
Is there anything you would tell people to watch out for with this mattress?
This is another bed where I don’t think heavier sleepers will get the support they need. They should take a look at our roundup of the best mattress for heavier sleepers to find a firmer and more supportive option.
Learn more in our full Helix Midnight mattress review. You can also click here to get the best deal or see our best mattress for side sleepers page for more options.
Brooklyn Bedding Signature Hybrid – Best Mattress-in-a-Box for Combination Sleepers
The Brooklyn Bedding Signature Hybrid mattress combines a foam comfort layer and sturdy coils. This combination of materials makes it bouncy and easy to move around on. It comes in three firmness levels, and we recommend the Medium model for most back sleepers. It’s a great choice for shoppers who are looking for a new mattress on a budget. For more information, check out our video review.
What our tester says:
“Given that the Signature Hybrid has some excellent bounce, I’d highly recommend this mattress for combination sleepers who often change positions multiple times throughout the night. I also think the Signature Hybrid could be a great fit for couples. You shouldn’t be overly disturbed by a restless partner on this bed, and it has nice, firm edge support.” – Nichole Mondshein, lead reviewer and staff writer
Expert Opinion
When we’re looking for the best bed-in-a-box for combination sleepers, our criteria is fairly simple: we need to easily be able to move around and switch positions on top of the bed. The Brooklyn Signature Hybrid does just that. This mattress is made using Hyper-Elastic Supreme Response Comfort Foam in its construction, which is a more responsive alternative to memory foam. This material helps lift the sleeper up and out of the mattress. This is what makes it easy for combination sleepers to move around without getting “stuck” in the bed.
As a hybrid model, the Brooklyn Signature Hybrid includes a support layer made of springs. Once again, these springs help bring bounce to the mattress, making it extra-responsive to movements from the sleeper. During our Rest Test, we were able to switch from sleeping on our back to sleeping on our stomach with ease, proving that combination sleepers should rest comfortable on the Brooklyn Signature Hybrid.
What Our Tester Says
How was delivery and setup?
As a brand, Brooklyn Bedding owns its own factory, so it was able to deliver the Signature Hybrid right to the doorstep of Sleepopolis’ mattress lab with no issue. The bed wasn’t too heavy, and the off-gassing smell only lasted for about a day.
How would you describe the firmness and feel of the mattress?
I found the Signature Hybrid to be a true medium-firm mattress. I got a decent amount of pressure relief at my joints and lower back, but also got enough of a lift for a neutral spinal alignment. I primarily recommend it for average weight back sleepers and side sleepers. I was also able to easily switch positions on its surface, which is why I recommend it for combination sleepers.
Is there anything you would tell people to watch out for with this mattress?
Sleepers who suffer from shoulder pain most likely won’t receive the pressure relief they need from the Brooklyn Signature Hybrid, as our pressure map showed yellow around the shoulders during side sleeping. For other options, check out our roundup of the best mattresses for joint pain.
Learn more in our full review of the Brooklyn Bedding Signature Hybrid. You can also click here to get the best deal or see our best mattress for combination sleepers page for more options.
WinkBed – Best Hybrid Mattress-in-a-Box
The WinkBed is a luxury hybrid mattress. It has a similarly supportive and sturdy feel to a traditional innerspring mattress, but upgrades like a Euro top and cooling Tencel cover give it a touch of modern luxury. Available in three firmness levels, there is a WinkBed for just about every sleeper. And a responsive and bouncy feel makes it a great pick for combination sleepers. Learn more in our video review.
What our tester says:
“If you like the feel of a traditional innerspring mattress, the WinkBed could work for you. Since this bed offered great pressure relief around my lumbar region, I’d also recommend it to folks who suffer from lower back pain.” – Nichole Mondshein, lead reviewer and staff writer
Expert Opinion
As a hybrid bed-in-a-box, the WinkBed combines a plush pillow top with ultra-supportive coils to create a luxury feel. The support layer includes sturdy coils with multiple support zones, so sensitive areas like the lower back should stay supported throughout the night, which is beneficial for back sleepers and those with back pain. The coils also provide the bounce that appeals to combination sleepers who need to switch positions easily during the night.
All of the foams used in the construction are free from harmful chemicals and heavy metals, as well as fiberglass. Also, the WinkBed’s coils are pocketed, so the spaces between them promote airflow and breathability. This allows the mattress to sleep cooler for longer.
Note: The WinkBed is available in several different firmness levels. We tested the Luxury Firm.
What Our Tester Says
How was delivery and setup?
I had no issues whatsoever with delivery, but I found the WinkBed to be one of the heavier bed-in-a-box mattresses out there because of all the springs in its construction. I recommend asking someone to help you set it up. It also had a faint off-gassing smell that went away after 24 hours.
How would you describe the firmness and feel of the mattress?
The Luxury Firm model of the WinkBed had a bouncy and responsive feel that made it easy to move around while I was resting on it. I think this makes it a good fit for combination sleepers. I gave it a score of 7 out of 10 on our mattress firmness scale, so it’s definitely on the firmer end of the spectrum. I think average weight stomach sleepers and back sleepers should get the firmness and support they need for a neutral spinal alignment.
Is there anything you would tell people to watch out for with this mattress?
I didn’t think the WinkBed was pressure-reliving or contouring enough while I was on my side. Strict side sleepers may want to look for a softer mattress, as these folks need added contouring around their joints in order to sleep without pain. They should opt for the Softer WinkBed model, or check out our roundup of the best mattresses for side sleepers for some better options.
Learn more in our full WinkBed mattress review. You can also click here to get the best deal, or take a look at our roundup of the best hybrid mattresses for more options.
Nolah Evolution – Best Mattress-in-a-Box for Back Sleepers
The Nolah Evolution’s hybrid construction offers the cushioning of memory foam with the responsiveness of coils. The Luxury Firm model is a good option for side and back sleepers due to its medium-firm feel, though there are Plush and Firm versions as well. Those who share a bed may also appreciate its low motion transfer, so you won’t be disturbed by a partner’s movements and its solid edge support to allow you to maximize surface area. For more information, check out our video review.
What our tester says:
“I laid down to rest on this mattress on my back — my primary sleep position. I felt comfortable, but also appreciated the cozy, plush top of the bed. After some time lying on my back, I switched over to my side. I didn’t find this position quite as comfortable, as I did feel some slight pressure buildup in my shoulder.” – Amelia Jerden, senior staff writer
Expert Opinion
The Nolah Evolution mattress is a bed-in-a-box hybrid, so it uses a combination of foam and coil layers to create a mix of support and comfort. When lying down on it, our mattress testers sank into bed a little bit, but they didn’t feel like they were being swallowed up by the mattress. This shows that the Nolah Evolution works well for back sleepers needing the optimal balance of comfort and support. They should receive cushioning at the lower back from the foams, but their spine should stay in a neutral alignment from the springs. This combination will also be helpful to sleepers who suffer from back pain and need more support around their lumbar region.
The Nolah Evolution mattress is available in three different firmness levels: Plush, Luxury Firm, and Firm. We tested the Luxury Firm and found it to be a 6.5 out of 10 on our mattress firmness scale, which is our standard for medium-firm. This allows the Nolah Evolution to have the perfect combination of durability and pressure relief.
What Our Tester Says
How was delivery and setup?
I found the Nolah Evolution’s delivery to be fast and convenient, with no issues. For a hybrid mattress, it also wasn’t too heavy. It did have an off-gassing period and took about 24 hours to fully expand.
How would you describe the firmness and feel of the mattress?
I tested out the Luxury Firm model and found it to be a true medium-firm to bed — a 6.5 out of 10 on our mattress scale (the industry standard for that firmness level). I got some strong support for my spine, while also getting a little bit of contouring from the mattress’s proprietary foams. I felt the most comfortable sleeping on my back and side.
Is there anything you would tell people to watch out for with this mattress?
I think the Nolah Evolution could feel too soft for strict stomach sleepers. It may not lift their hips high enough to keep them in line with their shoulders (a key to maintaining a healthy spinal alignment). These sleepers should take a look at our roundup of the best mattresses for stomach sleepers to find some firmer options.
Learn more in our full Nolah Evolution mattress review. You can also click here to get the best deal, or take a look at our best mattress for back sleepers page for more options.
Bear Elite Hybrid – Best Soft Mattress-in-a-Box
The Bear Elite Hybrid uses foam and coils for a mix of support, cushioning, and cooling. While designed for athletes prioritizing wellness and recovery, sleepers of all activity levels can enjoy the many luxurious features. Enjoy zoned support for targeted relief, an “on top of” feel allowing for ease of movement, and cooling features throughout. For more information, watch our video review.
What our tester says:
“I’d recommend the Bear Elite Hybrid for most back and stomach sleepers.I think these sleepers will get the needed pressure relief and contouring around the lower back and hips. This mattress does a wonderful job at offering body contouring while still helping the sleeper stay elevated and lifted as well. The layers of foam should provide comfort while the coil system should offer lots of support.” – Nichole Mondshein, lead reviewer and mattress tester
Expert Opinion
Many sleepers love the feel of a cradling soft mattress that really allows them to sink into its layers. However, these folks still need support and durability in order to avoid pain and discomfort. That’s where the Bear Elite Hybrid comes in. This mattress is the Bear brand’s “ultra-luxurious” model, so it combines pressure relief and body-contouring with stability and support for the best of both worlds. The Bear Elite hybrid also comes in three different firmness levels (Soft, Medium, and Firm), so sleepers really can tailor this bed to their needs and preferences.
The Bear Elite Hybrid scored a 6 out of 10 on our mattress firmness scale, making it softer than the industry average for a medium firm. With that in mind, side sleepers who need extra pressure relief and contouring along their shoulders and hips should find it on the Elite Hybrid. However, the hybrid nature of this soft mattress makes it great for back sleepers as well. These coils keep the spine elevated, and therefore aligned.
What Our Tester Says
How was delivery and setup?
Delivery was smooth for the Bear Elite Hybrid. The mattress does way 110 pounds, and I found it to be pretty heavy. So I suggest getting a friend or family member to help you move it inside and set it up. Since it’s a bed in a box, it may have to undergo a 24- to 72-hour off-gassing period.
How would you describe the firmness and feel of the mattress?
For a hybrid mattress, I found the Bear Elite to be pretty soft — about a 6 out of 10 on the mattress firmness scale. At the same time, it had a good amount of responsiveness, which made it easy for me to move around. In addition to being a natural fit for side sleepers, I think it’s comfortable for back sleepers and combination sleepers who need to change sleeping positions.
Is there anything you would tell people to watch out for with this mattress?
I think stomach sleepers may not be the best customers for the Bear Elite Hybrid because of how soft this mattress is (hence the superlative). These sleepers might want to find a firmer mattress that can lift their hips in line with their shoulders. Check out our roundup of the best firm mattresses if this sounds like you.
Learn more in our full Bear Elite Hybrid mattress review. You can also click here to get the best deal or see our best soft mattress page for more options.
Emma Original – Best Memory Foam Mattress-in-a-Box
The Emma mattress is an all-foam bed, meaning that it includes four layers of foam in its construction and it doesn’t include any coils or springs. However, these are not all layers of memory foam (which you might have been thinking). Instead, the Emma uses Point Elastic Airgocell foam, HALO memory foam, and HRX (High Resiliency Extra) Supreme Foam throughout its build. These dense foams create a firm mattress, which is actually uncommon for this kind of bed. Because of this firmness, the Emma is a good fit for back, stomach, and combination sleepers who like more of an “on top” feel to their mattress. Check out more in our video review.
What our tester says:
“I think the Emma is a great choice for back sleepers. Although this is an all-foam mattress, it should have the right combination of comfort and support that these folks need. Stomach sleepers should also find the support they need.” – Nichole Mondshein, lead reviewer and staff writer
Expert Opinion
The Emma Original is a unique bed-in-a-box because, despite being made entirely of foam, it offers a ton of support and a firm feel. The Emma even scored a 7 out of 10 on our firmness scale, making this mattress slightly firmer than average. In general, all-foam mattresses have difficulty in several areas, including cooling, sex, and edge support. However, the Emma changes the stigma around regular memory foam mattresses.
The Emma Original has features that make it one of the best all-foam mattresses for cooling. These include a breathable cover and Airgocell poly foam in its construction. It’s also made with an open-cell structure that promotes airflow and helps regulate the sleeper’s temperature. As for edge support, our mattress testers felt that the Emma did an impressive job holding up their weight on the edge of the mattress. This is ideal for partners who want to spread out on their mattress without fear of sinkage or sagging.
What Our Tester Says
How was delivery and setup?
There were no issues with delivery, and the foam construction meant that the Emma wasn’t too hard for me to move. That said, it’s always a good idea to have someone else on hand to assist with any heavy lifting. The Emma also had an off-gassing period, but the smell should go away within 24 to 48 hours.
How would you describe the firmness and feel of the mattress?
This is a firm mattress that, despite the foam construction, definitely gave me more of an on-top-of-the-bed feel. It featured a moderate level of body contouring and sinkage, but its Airgocell layer balanced things out on top. I was most comfortable while sleeping on my back and my stomach. I felt supported, and my spine was neutrally aligned.
Is there anything you would tell people to watch out for with this mattress?
Heavier sleepers need more support than most, and I don’t think they’ll find it in the Emma. I recommend they check out the best mattresses for heavier sleepers.
Learn more in our full Emma Original mattress review. You can also click here to get the best deal or see our best memory foam mattress page for more options.
Titan Plus – Best Mattress-in-a-Box for Heavy People
The Titan Plus mattress is a durable mattress made with heavy sleepers in mind. It’s firm and features heavy-duty coils and Titanflex foam that makes it bouncy and easy to move around on. We think that heavy back sleepers and stomach sleepers should be especially comfortable. For more information on the Titan Plus, check out our video review.
What our tester says:
“I think the Titan Plus lives up to its name as a good mattress for heavier sleepers. It will offer them the deep compression support and durability they need.” – Nichole Mondshein, lead reviewer and staff writer
Expert Opinion
With a firmness of 7.5 out of 10 and a support layer of 961 TitanCaliber encased coils, each measuring six inches tall, the Titan Plus is one heavy-duty bed-in-a-box. In fact, it was designed with heavy people (those over 250 pounds) in mind. That’s why we brought in a colleague with a larger body type to test it out. He experienced the Titan Plus as slightly softer than we did, getting some contouring and pressure relief from the mattress’ two-inch comfort layer of proprietary TitanFlex foam.
As a firmer mattress, the Titan Plus is ideal for back and combination sleepers. Back sleepers should receive enough support for a neutral spinal alignment, and the on-top-of feel lets combo sleepers switch positions and move around easily on top of the mattress. All of this support doesn’t mean the Titan Plus sacrifices comfort; it includes a quilted top cover made of polyester and gel memory foam that adds immediate plushness for the sleeper so they don’t feel like they’re sleeping on a plank.
What Our Tester Says
How was delivery and setup?
There were no issues with the delivery of the Titan Plus, but remember that this is an extra-heavy bed due to its taller height, multiple layers, and reinforced materials. I recommend you definitely get someone to help you move it into your home, then place it in a well-ventilated room for at least 24 hours to help dissipate the off-gassing odor.
How would you describe the firmness and feel of the mattress?
I found this to be a very firm bed, and it will be even firmer to anyone under 250 pounds. If you’re a heavy sleeper, I think the Titan Plus will be most comfortable for back sleeping and stomach sleeping.
Is there anything you would tell people to watch out for with this mattress?
Lightweight sleepers under 130 pounds may not like the Titan Plus because of how firm it is. No matter which sleeping position they prefer, they’ll most likely want a softer mattress with more pressure relief overall. These sleepers can take a look at our roundup of the best soft mattresses.
Learn more in our full review of the Titan Plus. You can also click here to get the best deal, or take a look at our best mattress for heavy people page for more options.
Birch Natural – Best Organic Mattress-in-a-Box
The Birch Natural is a latex mattress utilizing individually wrapped coils for added support. This mattress specializes in cooling and responsiveness, and the firmer nature suits back and stomach sleepers well. Perhaps the most special part about this mattress is the material quality. Not only is the Birch organic, but it has also earned multiple certifications for safe production and materials. For more information, check out our video review.
What our tester says:
“One of my favorite things about the Birch is how cooling it is. I think any hot sleeper will be satisfied by this breathable bed. It’s definitely one of the most cooling mattresses available thanks to its wool and latex layers. These cooling materials also make it one of my favorite organic mattresses.” – Madison Schaper, Sleepopolis staff writer
Expert Opinion
It can be tricky selecting the best organic bed-in-a-box, as many companies throw around the terms “organic” and “natural” rather loosely. That’s why we always start with the materials. Are they actually environmentally friendly? In the case of the Birch Natural, they very much are. A flame-retardant, organic cotton cover sits atop a comfort layer of organic wool. After that comes an 11-inch Talalay latex layer that’s Greenguard Gold certified, so it won’t release high levels of chemical emissions or volatile organic compounds. For support, there’s a pocketed coil system and an organic wool batting.
Not only do these materials make the Birch Natural a great fit for eco-friendly shoppers, but they also allow it to stay cool throughout the night. The pocketed coil system used in the construction make it particularly breathable, which is helpful for hot sleepers and couples who want to wake up sweat-free. The natural wool used in the Birch Natural also prevents this mattress from trapping body heat, keeping the mattress cool and odor-free.
What Our Tester Says
How was delivery and setup?
The Birch Natural is created by Helix, and the brand promptly sent the mattress to our doorstep. Also, because it contains latex foam and not memory foam, it didn’t have a chemical aroma and didn’t need any time to off-gas.
How would you describe the firmness and feel of the mattress?
I found the Birch Natural to be about a 7 out of 10 on the mattress firmness scale, with a bouncy, on-top-of-the-bed feel. This is pretty typical of latex foam, which is a naturally responsive material. Combo sleepers should be able to easily switch positions, and I also thought it was comfortable for back sleepers and stomach sleepers.
Is there anything you would tell people to watch out for with this mattress?
I think side sleeper and sleepers suffering from hip pain will most likely need a softer bed than the Birch Natural. The longer I laid on the bed, the more pressure I felt on my hips and shoulders. Because of this, sleepers with hip pain might want to check out our roundup of the best mattresses with pillow tops to get some extra pressure relief.
Learn more in our full Birch mattress review. You can also click here to get the best deal or see our best organic mattress page for more options.
Other Bed-in-a-Box Mattresses We Tested
- Purple Mattress: Due to this bed’s stretchy and breathable polymer grid, we found it provides just enough sinkage at the hips, shoulders, and knees to take pressure off of the joints. While it offers impressive relief for light and average-weight sleepers, those falling on the heavier side likely won’t receive the same amount of support. Read our full review.
- Casper Nova Hybrid Mattress: During testing, we found this mattress had stellar pressure relief results for side sleepers on sensitive areas like the hips and shoulders. Since this mattress is focused on a softer feel, we don’t feel this mattress has enough firmness and support for heavier sleepers (250 pounds or more). Read our full review.
Who Should Buy a Bed-in-a-Box
There are a number of reasons why purchasing a bed-in-a-box is more convenient and practical than showing up to buy a mattress in-store.
Shoppers Who Want Several Options
With nearly 200 bed-in-a-box brands to choose from, buyers have more options than ever before. There’s a model for almost any budget and personal preference.
Variety in Price and Budget
The majority of bed-in-a-box brands are available exclusively online. The few that make their products available to try out typically do so through the brick-and-mortar stores of other companies. Without showrooms, salespeople, and other overhead expenses, beds-in-a-box often cost less than traditional models.
For Convenience
Browsing beds-in-a-box, accessing detailed product information, and reading reviews online can be done anytime, and is typically less time-consuming than traditional brick-and-mortar shopping.
Privacy
Shopping for a bed-in-a-box online lets buyers bypass the usual sales process and browse in privacy. This can be preferable for people who like to shop without the presence of salespeople.
Risk-Free Trial Period
Bed-in-a-box brands typically offer a generous sleep trial period for testing out their products. Trial periods can range from a few months to a year.
Free Shipping & Returns
Most bed-in-a-box companies include free shipping and delivery of their products in the United States. Buyers in Alaska and Hawaii may need to pay an additional shipping charge. Shoppers looking outside the US may have a harder time finding a mattress in a box, but they can still find excellent online mattresses. Check out our top picks for the best mattresses in Canada to learn more.
Who Shouldn’t Buy a Bed-in-a-Box
Just because they’re popular doesn’t mean they’re for everyone.
No Option to Try-Before-You-Buy
The majority of bed-in-a-box models aren’t available to test out before purchasing, which may be a downside for some people, especially those trying out a new brand or type of mattress.
One thing to note is that most bed-in-a-box companies offer great trial periods, warranties and return policies so this has become less of a fear.
Heavy People might Lack Support
Certain standard beds-in-a-box may not be appropriate for heavier people, couples of above-average weight, or others who need more durable support. But there are plenty of bed-in-a-box models designed specifically for heavy people. Check out my top picks for the best mattress for heavy people.
Off-Gassing
Some bed-in-box models release volatile organic compounds (VOCs) when first unboxed. This odor can take a few days days to fully dissipate.
Hot Sleepers
If your bed-in-a-box is made from conventional memory foam without gel or other cooling properties, it may sleep hot. A bed-in-a-box made from latex or a cooling memory foam may be a better choice for warm sleepers. Keep in mind this is also the case with non-boxed mattresses. See my top picks for the best cooling mattress.
History of the Bed-in-a-Box
As outlined in the intro, mattress shopping has expanded from showrooms to computer screens, and with this movement, the bed-in-a-box was born. Although its beginnings are traced to roughly 20 years ago, the bed-in-a-box business really only started booming in the last 10 years. To understand the entirety of bed-in-a-box history, there are two major players: Bill Bradley, and the brand Casper.
Bill Bradey
The CertiPUR-US program, associated with the very materials certification so many bed-in-a-boxes have, shares a story on its website saying that it all started in 2004 with a man by the name of Bill Bradley. Bradley’s desire to find a way to make mattresses deliverable to customers’ homes by popular transport companies eventually snowballed into the creation of the Bed-in-a-Box company, followed by the very first Bed-in-a-Box delivery in 2006 (1).
Casper
Casper is one of the most renowned mattress manufacturers of all time. It had its start in 2014, and is often credited with highly popularizing beds-in-a-box to the high-level e-commerce market we know today. If you’re interested in Casper mattresses, feel free to browse our Casper Original review or our Casper Mattress Comparisons page.
More Beds Arriving In Boxes
These days, more than 12 percent of mattresses sold show up on the buyer’s doorstep in a box, ready to unpack and unroll. Skip down to the how to unbox section to learn more about the process.
Today, bed-in-a-box company websites usually offer in-depth descriptions, reviews, and pictures of their products, as well as live chat with customer service specialists. Purchasing a mattress has never been easier, and can take a fraction of the time it once did.
Things to Consider When Buying and How we Test a Bed-in-a-Box
In addition to doing your research and vetting the mattress company you choose to buy from, you’ll also want to consider whether or not a mattress will meet your specific sleep needs. Take a look below to see what you should consider before purchasing any mattress, boxed or not. You can also check out our How to Choose a Mattress guide for more in-depth information.
Firmness
Beds-in-a-box have different firmness levels that range from soft to very firm. As a general guide, memory foam mattresses are softer to medium-firm, and mattresses that contain coils are firmer. When we test mattresses in studio, we put each mattress on our firmness scale that ranges from 1-10 with 1 being the softest mattress you’ve laid on and 10 being the firmest. A 6.5 is considered a true medium-firm mattress.
We recommend side sleepers choose a softer mattress (3-6 on our scale) so they feel more pressure relief around their shoulders and hips. Stomach sleepers will need a firmer mattress (5-7) to feel supported and lifted.
Sleep Position
Firmness is important when it comes to sleeping position as well. A medium-soft to medium-firm mattress is generally recommended for side sleepers to relieve pressure in the shoulders and hips, whereas a firm mattress can help support the neck and promote proper spinal alignment for stomach sleepers. Back sleepers typically do best on a medium-firm mattress that supports the spine while cushioning the shoulders and pelvis. Combination sleepers are the most flexible when in comes to firmness levels but we recommend staying in the 6.5, medium-firm mattress range to feel supported throughout the night but still feel good pressure relief in the hip and shoulders.
Mattress Thickness
Most bed-in-a-box models run from about six to 14 inches thick. Typically, the thinner the mattress, the firmer it will feel. Thickness also helps to determine needed base support. If your mattress is on the thicker side, a platform alone may be sufficient, while a thinner mattress may feel best on a box spring or other elevating layer.
Contouring and Pressure Relief
Pressure relief is a measure of how evenly distributed your weight will be on any given mattress. Even weight distribution helps prevent pressure buildup in areas like the hips, shoulders, and lower back. If you struggle with pain, a mattress that offers body-contouring and pressure relief can be very helpful. Body-contouring beds conform to the shape of your body to provide pressure relief around sensitive joints like the shoulders and hips. These beds have a cradling, hug-like feel that many side and back sleepers find comfortable. Memory foam mattresses match particularly well with sleepers on the hunt for a body-contouring feel.
Generally, side sleepers prefer pressure-relieving beds made with memory foam or other soft foam layers, while stomach sleepers often do better on less pressure-relieving mattresses with innerspring or hybrid builds. Back sleepers generally do best on something in between.
When testing mattresses, we use a pressure map to determine what pressure points each bed has. We roll this pressure map mat across a mattress and lay on it in all sleeping positions. The technology then gives us a thermal pressure map so we can see where pressure is relived. As you can see, green and blue on the map represent good pressure relief, where red and orange show poor pressure relief. Since a lot of bed in a box beds are memory foam, its crucial to make sure you are still getting the relief you need in your new mattress.
To find out how we test pressure relief, see our Sleepopolis Mattress Methodology.
Edge Support
Edge support refers to how well the sides of a mattress hold up under your weight. A mattress with good edge support will feel larger, as you can sleep all the way on the side of the bed without feeling like you’re going to fall off. Great edge support is important for couples who need all the space, seniors or anyone with chronic pain who need extra help getting out of bed and lastly for anyone sharing a bed with kids, or pets. It also prevents sagging, which adds to your mattress’s overall durability.
We test for edge support simply by laying and sitting on the edge of the bed and seeing how supported we feel. We also use a yard stick to determine how deep the mattress sinks when sat on the edge. Edge support is especially important to seniors who need extra support when getting out of bed.
Size
Beds-in-a-box range from crib size to California king. Some sellers don’t offer exchanges for a smaller or larger mattress, so be sure to measure your bed frame, box spring, and bedroom before buying. And remember, larger may be better if you share a bed with a partner, children, or pets.
Cooling
If you’re looking at buying a bed in a box mattress, you might be concerned if they perform as well as their more expensive counterpart mattresses. Well we put each mattress to the test for you. We use a temperature control gun to measure the cooling properties of each bed. After our testers lay on the bed for several minutes, we measure how long it takes for the mattress to release the heat and therefore regulate your body temperature. We consider an 8 degree change or under to be good cooling, and a change of 5 degrees and under to be great cooling. Sleeping on a cooler bed will help you sleep through the night much more comfortably. Also be sure to check out each mattress’s construction and be on the look out for breathable materials, coils, cooling gels… all these materials will help you stay cool at night.
Shipping & Delivery
Most beds-in-a box are usually shipped free in the contiguous U.S. and often arrive by ground delivery via UPS, Fed-Ex, or the Postal Service. Shipping times vary according to manufacturer and stock levels of a particular product. Expedited shipping is often available for an additional charge. Shoppers can also pay extra for a white glove delivery, which usually includes delivering, unboxing, setting up the new mattress and removing the old one if necessary.
A boxed queen size mattress weighs around 75 to 80 pounds, while a king can weigh over 100 pounds. Box dimensions can range from around 18 inches by 18 inches by 42 inches to 20 inches by 20 inches by 44 inches.
How to Get Rid of Your Old Mattress?
Several brands featured on this list have options for a mattress removal service when your new one is dropped off, however if you are looking to get rid of your mattress yourself here are a few tips.
- Drop it off at you local recycling center
- Use local moving companies like LoadUp and College Hunks for a fee
- Donate your mattress to a local donation center for it to have a second life with a family who needs it.
Budget
One of the benefits of a bed in a box is the variety in price. Whether you’re looking for a luxury mattress or a budget friendly pick, there is a bed in a box that will work for you. To avoid hidden fees or surprises, check carefully before completing your purchase. Some buyers may need to pay sales tax or recycling fees in addition to the cost of the mattress.
How Much Should You Spend on a Mattress?
We suggest you decide your mattress based on your sleeping position, body type, and lifestyle however if you need to stick to a budget, a higher price tag will not necessarily mean a better mattress. There are several quality mattresses under $1000 however we suggest you look for mattresses priced $1000-$1800 that fit your mattress needs and have great warranty, sleep trial and return policies so you can have peace of mind when making this large purchase.
Off-Gassing
A bed-in-a-box can take up to two days to fully expand, though many expand in less time. Read our full unboxing guide to learn more.
Some mattresses give off a scent when first unpackaged. The odor is also known as off-gassing and is caused by the release of volatile organic compounds, or VOCs, from the mattress materials. Other sources of VOCs include paint, gasoline, and plants. Some VOCs are hazardous, whereas others are relatively harmless. Studies are needed to determine whether VOCs released by bed-in-a-box mattresses are harmful over the long term.
It’s important to keep in mind that beds-in-a-box can sometimes take a few hours or days to go through their unboxing and off-gassing periods. This is how long it takes for your mattress to fully decompress into the shape it is supposed to be, and how long it takes for your mattress to get rid of any gasses that got stuck when the mattress was condensed into the box. This should take less than 24 hours, but it’s good to be prepared for your mattress to look slightly different than it did on the website.
To help minimize the odor from your new mattress, ventilate the bedroom as much as possible during the expansion process. Waiting until most of the odor is gone before sleeping on the mattress can help prevent headaches and breathing issues.
If you’re wanting to learn more, see our guide on How Long to Off-Gas a Mattress.
Certifications to Look our For the Best Memory Foam Bed
Check to see if the foams your mattress is made of are CertiPUR-US® Certified. CertiPUR-US® Certified foams are free of harmful chemicals and heavy metals, and are better for the environment.
Types of Boxed Mattresses
Beds-in-a-box are made of materials that can expand without damage after being rolled and compressed. Most are constructed from memory foam, latex, and/or high-density poly foam, and may contain internal coils for additional support.
Memory Foam
Many beds-in-a-box are all-foam, and use a combination of high-density poly foam for support and memory foam (or another comfort foam) for pressure relief. Memory foam conforms to the body and has a plush feel. Layers of memory foam allow for gradual sinkage and may sleep warmer than other materials. Memory foam is a great choice for people who like to feel cradled by their mattress. Check out our best memory foam mattresses of 2024 review.
Latex
Latex is a natural material derived from the rubber tree. It has a bouncy feel and offers less sinkage than memory foam. Natural latex is an eco-friendly material, which makes a latex mattress a great option for folks looking for the best organic mattress.
Hybrid
Some bed-in-a-box models use a hybrid construction that combines a foam or latex layer (or both) with internal coils. Coils can offer supportive internal structure to a beds-in-a-box, but must be small and light enough to be compressed for shipment.
Innerspring
Innerspring mattresses have a more traditional feel and are usually mostly composed of wrapped coils. Those searching for the best innerspring mattress typically want something that’s bouncy and on the firmer side.
Does Vacuum-Packing Impact the Durability of Foam Layers?
Bed in a Box mattresses are vacuum sealed and packed in order to make shipping easier. Vacuum-packing can impact the durability of foam layers in a mattress because of the tight compression of the construction. This can lead to structural loss and comfort over time, making bed in a box durabilities shorter. The vacuum pack can cause some unevenness and sagging but in general, properly packed, bed in a box mattresses are great options for easy shipping.
Returns, Exchanges, and Warranties of Bed in a Box Mattresses
Returns
The return policy is crucial for beds-in-a-box, which are typically purchased based on reviews and descriptions rather than personal experience. Most bed-in-a-box manufacturers offer a 100-night trial period, which allows buyers to try out a mattress for more than three months before returning it. A few manufacturers offer a full year trial period. Return shipping is usually free.
Before buying a bed-in-a-box, make sure you understand how returns work. In some cases, you may be required to box up your mattress and prepare it for shipment, while in others a company representative will take care of the process. Keep careful track of how long you’ve had your mattress to avoid missing the return or exchange window.
Exchanges
Many companies offer exchanges during the trial period in addition to returns. The exchange process will vary according to the manufacturer, but will often require contacting a customer service representative by phone, email, or chat to make arrangements for pickup or return shipping, delivery of the new item, and additional payment or partial refund.
Warranties
A warranty is important for both traditional and beds-in-a-box. According to the Federal Trade Commission, a warranty guarantees that a manufacturer stands behind a product’s performance for a set period of time. Many mattress companies offer at least a 10-year warranty on their beds, but certain brands (like Nectar) offer lifetime warranties.
For more, see our guide on How to Return a Mattress.
Break-In Periods
Some bed-in-a-box companies require buyers to keep the mattress for a certain period to “break it in” and allow adequate time to adapt to the feel of the materials. Once this break-in period is over, a return can be initiated if necessary.
Are Bed-in-a-Box Mattresses Compatible with Adjustable Bases?
Adjustable bases have gotten very popular in the last few years and for good reason. Adjustable bases allow for a lot of firmness customization and is especially great for couples who have different sleep preferences and for anyone with chronic pain who would benefits from their legs, back or hips lifted for pressure relief. Most bed in a box mattresses are adjustable base friendly but it’s important to check for each individual mattress. Memory foam, latex and hybrid mattresses often work best for adjustable bases because of their flexible construction. Innerspring mattresses are much less supple because of the coil base construction and will perform worse when place in an adjustable bed.
Memory Foam Mattress Accessories
How to Unbox Your Bed-in-a-Box
Boxed mattresses usually come wrapped in vacuum-sealed plastic sheeting along with additional binding material to keep the product from unrolling. Additionally, most manufacturers include unboxing instructions with a bed-in-a-box, but we’ll outline the basics below.
1. Because even a partially expanded bed-in-a-box can be heavy and cumbersome, most manufacturers recommend taking it to your bedroom and placing it on your box spring, foundation, or platform before unboxing it. We also recommend grabbing a friend to help you with this process.
2. Next, you’ll want to remove the mattress from its box, and prepare to remove the outer layer of the plastic packaging.
3. Roll the mattress out across the platform as you remove the wrapping. Position it as you would if the mattress were fully expanded.
4. When opening the inner vacuum-sealed portion of the plastic packaging with scissors or a knife, care should be taken not to cut or damage the mattress.
5. Once the plastic packaging is removed, the mattress begins to expand as it regains air pressed out during the compression process.
Bed in a Box Frequently Asked Questions
How will I know when I need a new mattress?
Most mattresses last about seven years. Mattresses that are less supportive or made of less durable materials can sag or flatten in less time. Signs that it’s time to replace a mattress include the following:
- The mattress becomes uncomfortable, lumpy, or loses support along the edges
- You wake up feeling achy or stiff
- Rotating the mattress no longer helps
- You’re heavier or lighter than you used to be, or your mattress needs have changed
- Your bed has a different odor or causes eye or respiratory irritation
How quickly do I need to unbox my new mattress?
Most bed-in-a-box manufacturers recommend taking your mattress out of the box within 30 to 60 days to prevent damage from long-term compression.
What do bed-in-a-box manufacturers do with returned mattresses?
Many states do not allow manufacturers to resell mattresses once they’ve been used. Most beds-in-a-box that have been returned are donated or recycled.
Do you need a base or box spring for a bed-in-a-box?
Depending on what type of boxed mattress you purchase, there may be restrictions on what type of base you’ll need to place it on. Most mattresses these days are compatible with everything from box springs to adjustable bases, so you most likely won’t need to purchase something new. But be sure to check out your new bed’s product information and warranty to ensure you’re placing your new mattress on the right foundation.
Can you flip a bed-in-a-box?
Generally, no. We don’t recommend flipping a bed-in-a-box unless the brand clearly states that the mattress is flippable, such as the Plank Firm or the Layla Original. If your bed-in-a-box isn’t flippable but you still want to help prolong its lifespan, we recommend rotating it head to foot, or 180 degrees, twice a year.
What are the risks of boxed mattresses?
There are a couple disadvantages of purchasing a bed-in-a-box. The most obvious one is that in most cases, you won’t be able to test out the mattress before you buy it, but luckily many brands offer sleep trials so you don’t have to fully commit. Secondly, boxed mattresses often off-gas, and though it’s harmless, it’s inconvenient to wait a couple days for the odor to dissipate.
How We Chose These Mattresses
Our team of Certified Sleep Science Coaches has reviewed more than 300 products in our mattress lab, running each one through tests such as pressure-mapping and measuring motion transfer with a seismometer. From there, we give every bed an overall score based on materials, comfort, support, cooling, and edge support. We also factor in brand performance with categories such as value and warranty.
Since the term “bed-in-a-box” encompasses such a wide variety of mattresses, we placed a huge emphasis on the overall score. Of the 10 products included in this roundup, all of them have an overall score of 4 out of 5 or higher. Jump back to our mattress picks or click here to learn more about our methodology.
The Best Mattress-In-A-Box 2024
| Mattress | Best For | Price (Queen) | Coupon | Review |
|---|---|---|---|---|
| Nectar | Overall | $1,099 | Nectar Coupon | Read Our Review |
| DreamCloud | Couples | $1,332 | DreamCloud Coupon | Read Our Review |
| Helix Midnight | Side Sleepers | $1,332 | Helix Coupon | Read Our Review |
| Brooklyn Bedding Signature Hybrid | Combination Sleepers | $1,332 | Brooklyn Bedding Coupon | |
| WinkBeds | Hybrid | $1,799 | WinkBeds Coupon | Read Our Review |
| Nolah Evolution | Back Sleepers | $2,499 | Nolah Coupon | Read Our Review |
| Bear Elite Hybrid | Soft | $2,305 | Bear Coupon | Read Our Review |
| Emma Original | Memory Foam | $1,053 | Emma Coupon | Read Our Review |
| Titan Plus | Heavy People | $1,249 | Titan Coupon | Read Our Review |
| Birch Natural by Helix | Organic | $2,123 | Helix Coupon | Read Our Review |
Sources
1. The History of Beds in Boxes. CertiPUR-US. December 8, 2023. Accessed February 27, 2024. https://www.ncbi.nlm.nih.gov/books/NBK553107/.