We have affiliate relationships where we are paid a commission on sales through some of our links. See our disclosures.

Amerisleep AS4 Mattress Review

Are you looking for a medium-soft, high-quality, all-foam mattress? Then you’ll want to take a look at the Amerisleep AS4. The second softest bed in the Amerisleep arsenal, this mattress has a deep top layer of pressure-relieving memory foam, with an open-celled construction for added cooling. 

But is it all it’s cracked up to be? Today, I’ll be putting the AS4 to the test, measuring how well it relieves pressure, feels for different sleepers, absorbs motion, and more. Let’s get started!

If you’re in a pinch for time, have no fear, check out my full review summary here.

Save 30% + Free Gifts with Code AS30
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress

On the softer side, the AS4 could be a great pick for side sleepers! Get 30% off with code AS30.

Is the Amerisleep AS4 a Good Mattress for You? 

How will you know if the AS4 is right for you? After testing out this mattress myself, I’ve gathered my top recommendations based on the features that will best suit certain sleepers, as well as who should steer clear. 

Who I recommend the Amerisleep AS4 mattress for

  • The AS4 is a good option for side sleepers, who will appreciate the extra cushioning and plush feel.
  • I’d definitely recommend this mattress to couples. The AS4 performed very well on both the edge support and motion transfer tests, both important for sleeping with a partner, which you’ll find more details on later in the review. 
  • Finally, this would be a home run for those who prefer a memory foam feel. With its outer, 4-inch, memory foam layer, the AS4 will provide the plush, body-contouring that these sleepers love.

Who I don’t recommend the Amerisleep AS4 mattress for

  • I think that all of my stomach sleepers out there will prefer a firmer mattress, since the all-foam construction of this mattress may cause the hips to sink, throwing them out of alignment with the spine. I’d suggest taking a look at the firmer AS1 or AS2
  • I would not recommend this Amerisleep mattress to heavier sleepers either. The many layers of memory foam would cause them to sink too deep into the mattress, potentially causing it to “taco” around them. I’d steer them to our best mattress for heavy people roundup instead.

How Firm is the Amerisleep AS4 Mattress?

Different body types and sizes cause everyone to feel the firmness level of a mattress a little differently. With the help of a few additional testers’ opinions, we tested the AS4, which should help to give you a better idea of what you can expect from this mattress.

When I first pressed into the mattress, I felt the traditional memory foam feeling of the mattress contour to my hand. The comfort layer is relatively thick and has a slow response to pressure, so I could see the outline of my hand on top of the mattress when I removed it. When I applied more pressure with both of my hands, I was able to sink further into the comfort layer, but it was so thick that I didn’t really interact with the firm base. 

Amerisleep AS4 Hand Press
Pressing into the Amerisleep AS4 mattress

 A 6.5 out of 10 is generally considered to be the industry standard for medium-firm on the firmness scale, which was our average rating for the AS4. I was surprised to find a mattress with such a thick, top layer of memory foam to be medium-firm.

Amerisleep AS4 Mattress Performance 

We use a number of tools to determine who a mattress will be best for. We hone in on different sleeping positions and weights,  test for pressure relief, motion transfer, and how a bed will perform in important areas for couples.

Testing the Amerisleep AS4 Mattress in Different Sleeping Positions

There are a plethora of combinations in the world of sleepers, and they each have their own, unique criteria and needs when it comes to finding a new mattress. Everyone requires different amounts of support, so I’ve compiled a list of how this Amerisleep mattress experience may be for a variety of combinations.

Is the Amerisleep AS4 a Good Mattress for Light Sleepers (Under 130 lb)?

  • Light Back Sleepers – The thick layer of memory foam should create a good combination of softness and body-contouring for these sleepers.
  • Light Side Sleepers – I think that these sleepers will find that this Amerisleep mattress offers the proper amount of cushion they desire.
  • Light Stomach Sleepers – This sleeper will most likely feel the AS4 to be a touch firmer than it is. They may just hit that sweet spot with this medium-firm mattress, as they don’t need as much support as an average or heavier sleeper would.

Is the Amerisleep AS4 a Good Mattress for Average Weight Sleepers (130 – 250 lb)? 

  • Average Weight Back Sleepers – These sleepers should experience a good amount of weight distribution with this mattress, while some may experience a firmer feel, with a bit of added sinkage, the longer they lay on it.
  • Average Weight Side Sleepers – The thick layer of memory foam should be a good fit for these sleepers, as they need to  sink into the mattress a bit for added pressure relief.
  • Average Weight Stomach Sleepers – These sleepers generally require a firmer mattress to keep their hips from sinking and their spines aligned.  I would recommend taking a look at one of the firmer versions in the Amerisleep mattress line.

Is the Amerisleep AS4 a Good Mattress for Heavy Sleepers (over 250 lb)? 

  • Heavy Back Sleepers – These sleepers will find this Amerisleep mattress to be too soft. They’ll  sink too deep into the mattress and might feel  “trapped”. For options specifically targeted towards these body types, check out our top picks for the best mattresses for heavy people.
  • Heavy Side Sleepers – See above.
  • Heavy Stomach Sleepers – See above.

Amerisleep AS4 Mattress Pain Relief Performance

Instead of just describing how the AS4 feels I wanted to give a visual representation of where someone may feel pressure points while lying on the mattress. To do this I placed a pressure map on top of the mattress and lied on my back, side, and stomach. In the graphic below, pressure will be represented from blue (low pressure) to red (high pressure).

Amerisleep AS4 Pressure Map
Pressure map of the Amerisleep AS4 mattress

Back Pain – While laying on my back, I experienced some nice pressure relief and a bit of contouring at my lower back — all great things for back pain. White on my side, I got some nice sinkage at my hips and shoulders from the top layer of memory foam. However, on my stomach, I found my hips sinking out of alignment with my shoulders, which can worsen back pain.

Shoulder Pain – Back sleepers, you should find that this thick memory foam contours to your body with ease and sinks enough to offer pressure relief to the shoulders. For side sleepers, the memory foam sinkage should also offer some nice relief. Finally, to all my stomach sleepers, I think that the foam layer will offer some nice cushioning, but the mattress is too soft overall to be comfortable in this position. 

Hip Pain – Since sleepers with hip pain require an even softer mattress for relief, I think that both back and side sleepers will be happy as they sink into the soft, outer memory foam. However, stomach sleepers still need a firmer mattress; their hips will sink out of alignment on this plush bed, which could further hip pain. 

Amerisleep AS4 Mattress Performance for Couples

Sleeping with a partner opens up a lot more concerns about a new mattress. It is important for you to start looking at how motion transfers, what sex would be like, how much edge support it has, and what the cooling features are! Thankfully, we test for all of this at Sleepopolis. Let’s see how the Amerisleep AS4 did!

Motion Transfer 

If you plan on sharing your bed with a partner, then you’ll want to know what it will feel like when there is motion on the other side of the mattress. This test is helpful in showing the intensity of disturbance that is detectable from one side of the bed to the other.

For this test I dropped a 10-pound steel ball from heights of 4 inches, 8 inches, and 12 inches, to simulate someone changing positions or getting into bed, and measured the disturbance on the other side of the mattress. This should be pretty intuitive — the bigger the lines, the bigger the disturbance.

Amerisleep AS4 Motion Transfer
Motion transfer results for ball dropped from 4 inches, 8 inches, and 12 inches

The 4inch drop simulates someone rolling around in bed and shows a small amount of motion transferred across the mattress. While the 8 and 12inch drops cause higher levels of disturbance, these are still good results when compared to other mattresses I have reviewed. I credit the thick memory foam comfort layer with dampening the disturbance and isolating the motion of these drops.


A mixture of motion transfer and responsiveness is crucial for sex. In the case of the AS4, we’re working with thick layers of foam, which are pretty plush, and don’t offer much bounce. You need a bit of bounce to move around during sex, so overall I think that this mattress would be okay for sex, but it’s not the best I’ve seen.


Since two people on a mattress create more body heat than one, cooling is super important for couples. In addition to a poly foam layer that improves temperature regulation, hot sleepers will appreciate that this soft mattress also features Bio-Pur foam for optimal cooling comfort.

Edge Support

If you’re going to share a mattress, then you need to use the entire surface area; edge support is definitely something you are going to want to take a look at. Foam mattresses sometimes struggle to live up to the edge support of traditional innerspring mattresses, so I wanted to have a look at how I would feel near the side of the mattress.

Back sleeping on the edge of the Amerisleep AS4
Edge support while lying near the edge of the Amerisleep AS4 mattress

While lying on my back near the side of the AS4 I found that the feel of the mattress stayed the same on the side as at the center. The image above shows that when I moved to the edge of the AS4 there was some compression, which is expected out of a softer memory foam, but I found that I felt secure and that my weight wasn’t collapsing the side of the mattress. 

Side sleeping on the edge of the Amerisleep AS4
Edge support while lying on my side near the edge of the Amerisleep AS4 mattress
Save 30% + Free Gifts with Code AS30
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress

On the softer side, the AS4 could be a great pick for side sleepers! Get 30% off with code AS30.

What is the Amerisleep AS4 Mattress Made Of? 

The AS4 mattress is an allfoam construction, made of three layers, totaling 12 inches in height. The feel of the mattress comes from the thick comfort layer of memory foam, which allows the sleeper to sink deep into the mattress for pressure relief.

Amerisleep AS4 in bedroom
Corner view of the Amerisleep AS4 mattress

Cover – The cover for all of the mattresses in the Amerisleep line is made of a soft blend of polyester, Celliant and spandex. It’s a stretchy material that snaps back into place quickly, so you won’t have to worry about the cover bunching up when you change positions on the mattress. I should mention that there is some evidence that the Celliant cover provides some benefits for muscle recovery. I don’t have the expertise to go into detail on the science behind these studies, but if that interests you I recommend doing some research on the subject

In terms of the feel of the cover, I found that it had a bit of thickness to it, which made it pretty soft. As I pushed into the top of the mattress I could feel some airflow through the cover, which shows it has some breathability to help with cooling.

Comfort – The comfort layer of the AS4 is made of a 4 inch layer of memory foam. This layer will allow the sleeper to sink in for pressure relief and provide the classic memory foam feel of contouring to the body. Amerisleep uses a memory foam with an open-cell structure in all of their mattresses to aid in cooling of the mattress as memory foam can be known to trap too much heat at times. I should note that Amerisleep uses plantbased materials in their memory foams, which is eco-friendly and helps cut down on the use of petroleum in the construction.

Transition – Below the comfort layer is what Amerisleep calls the Affinity layer. It consists of a 1 inch layer of poly foam that has a convoluted (eggshell) design. This design creates space to allow air to flow through the mattress for improved temperature regulation and cooling of the mattress. This layer is a bit firmer so it acts as a transition layer between the comfort and base layers of the AS4.

Base – The base of the mattress is made of 7 inches of high density poly foam. This firm support layer acts as the foundation of the mattress and provides deep compression support to the sleeper. The base also provides the mattress with its shape and some durability to the overall structure.

Amerisleep AS4 Mattress Unboxing and Off-Gassing

Amerisleep recommends moving your new bed to the bedroom while still in the box, as it’s easier to mobilize in that state. You can then open up your compressed mattress and place it on the bed. Be sure to open up the plastic bag, allowing your new mattress to expand to its full size for up to 24 hours. After that, you’re ready to enjoy your new mattress!

Upon unboxing, this soft mattress may emit a smell after being compressed. This is nothing to worry about, just let the mattress sit for a few days and the smell should fade.

My Final Thoughts about the Amerisleep AS4 Mattress

Before we finish up this Amerisleep mattress review, let’s take a look at my final snapshot of the best and worst that the AS4 has to offer.

My favorite things about the Amerisleep AS4 mattress

I really liked the classic, memory foam feel here. The AS4 feels cloud-like as you sink into the body-contouring layers of foam. I also really enjoyed the pressure-relieving capabilities for side sleepers, as this mattress is  both soft and supportive. I also found that my weight was evenly distributed, and I could move with ease while sleeping on my back. Finally, I felt that this mattress had a good amount of both motion isolation and edge support, so that couples can fully utilize the entire surface area of their mattress.

My Amerisleep AS4 mattress complaints 

Though this is a great mattress for couples, one complaint I had was that lack of bounce. This makes it not the best option for sex. I also think this mattress wouldn’t do stomach sleepers justice, as they’ll likely find their hips sinking and throwing their spine out of alignment.

How Much Does the Amerisleep AS4 Cost? 

Check out our pricing chart for all of the available prices, sizes and dimensions that the Amerisleep AS4 comes in. They’ve got everything from twin to twin XL and California king to split king, so be sure to check it out.

Twin38" x 74" x 12"56 lbs$1,449
Twin XL38” x 80” x 12”62 lbs$1,499
Full54” x 74” x 12”79 lbs$1,649
Queen60” x 80” x 12"94 lbs$1,799
King76” x 80” x 12”119 lbs$2,099
California King72” x 84” x 12”119 lbs$2,099
Split King38" x 80" x 12" (x2)62 lbs (x2)$2,998

Save 30% + Free Gifts with Code AS30
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress

On the softer side, the AS4 could be a great pick for side sleepers! Get 30% off with code AS30.

Amerisleep AS4 Mattress Policies and FAQs

Does this Amerisleep mattress offer free shipping?

Yes, but only for orders within the continental United States.

Does the brand offer a trial period for this mattress?

Yes, they offer a risk-free, 100-night sleep trial.

Does this Amerisleep mattress have a warranty?

Yes, it has a 20-year warranty.

Is the Amerisleep AS4 mattress made in the USA?

Yes, it’s made in the United States.

How can I pay for this mattress?

Amerisleep accepts all major credit and debit cards, bank transfers from checking or savings accounts, and they also offer 0% APR financing.

Amerisleep AS4 Mattress Vs  

If you’re taking a look at Amerisleep’s AS4, you’re likely sizing up the competition. It’s  important to take a look at all of your options, so you’re well equipped to make that final purchasing decision. Today, we’re going to compare the AS4 to the Helix Midnight and Nectar Memory Foam beds.

Amerisleep AS4 Mattress vs Helix Midnight Mattress

Amerisleep AS4 Mattress vs Nectar Memory Foam Mattress

Other Models from Amerisleep

The Amerisleep has five models total, the others being the AS1, AS2, AS3, and AS5. I’ve compared the AS4 to each of its sister models down below.

AS4 Mattress vs AS1 Mattress

  • The AS1 has a thinner memory foam layer, no transitional poly foam layer, and a slightly thinner high-density poly foam base.
  • Being that it has those thick memory foam layers, the AS4 had more impressive results on the motion transfer test than the AS1.
  • Learn more in the full Amerisleep AS1 mattress review.

AS4 Mattress vs AS2 Mattress

  • The AS2 is the second firmest in the Amerisleep line, making it a good choice for back and stomach sleepers.
  • The AS2 has a 3-inch poly foam layer, giving it more bounce, vs the 1-inch in the AS4.
  • Learn more in the full Amerisleep AS2 mattress review

AS4 Mattress vs AS3 Mattress

  • The AS3 is Amerisleep’s medium-firm, and most popular, bed in their fleet.
  • Both mattresses are recommended choices for side sleepers and couples.
  • Learn more in the full Amerisleep AS3 mattress review.

AS4 Mattress vs AS5 Mattress

  • The AS5 is a 14-inch, luxury, memory foam mattress, and the softest amongst its sister models.
  • Different from the other Amerisleep models, this mattress has a foamy, 2-inch, Active Flex layer.
  • Learn more in the full Amerisleep AS5 mattress review.

That’s a wrap! Take a look at how the AS4 scored in our performance ratings down below.

Save 30% + Free Gifts with Code AS30
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress
Amerisleep AS4 Mattress

On the softer side, the AS4 could be a great pick for side sleepers! Get 30% off with code AS30.

Amerisleep AS4 Mattress
  • Materials
  • Comfort
  • Support
  • Value
  • Cooling
  • Edge Support
  • Sex
  • Smell
  • Company
  • Refunds
  • Trial
  • Warranty


The second softest mattress in the Amerisleep line, the AS4 has 4 inches of open cell memory foam for a comfort layer. This layer allows sleepers to sink deep into the mattress for great pressure relief, making it an excellent choice for side sleepers.

Logan Block
Logan is the content director of Sleepopolis, which means he not only reviews new mattresses every week, but also curates all the comparisons, best of pages, and video guides on the site. He takes a straightforward, honest approach to his reviews and endeavors to give viewers an objective look at each new product he tries out. Logan has perfected his method by personally testing over 200 different mattresses, so he’s not only able to discern the overall vibe of a specific bed, but to contextualize its feel within the bed-in-a-box market as a whole. When he’s not hopping on a new bed or working with our editorial team to whip up an engaging sleep education guide, you can find him reading books on world history, walking his dog Pepper, or searching for the best cheeseburger in New York City.