Amerisleep AS4 Mattress Review – Made For Side Sleepers?

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The all-foam Amerisleep AS4 is one of the softer mattresses in the Amerisleep line, which features five different models to accommodate all kinds of sleepers. The AS4 has a plush comfort top that could appeal to a variety of sleeping styles and body types.

Will this plush mattress give you the comfortable sleep you crave? Read on for our comprehensive Amerisleep AS4 mattress review to find out! We’ll detail the Amerisleep AS4’s firmness, feel, construction, and performance and lay out who might like this mattress and who might not.

30% Off
Amerisleep AS4
Amerisleep AS4
Amerisleep AS4

The Amerisleep AS4 is one of the brand's softest models and should be a great fit for side sleepers. Get 30% off the Amerisleep AS4 mattress by using code AS30

Amerisleep AS4 Mattress Overview

The Amerisleep AS4 comes in two versions – all-foam and hybrid. We reviewed the all-foam Amerisleep AS4 mattress, the brand’s second softest model. As we will discuss below, it features a very thick layer of Amerisleep’s proprietary Bio-Pur foam that offers excellent pressure relief.

The Amerisleep AS4’s design makes it a better fit for certain types fo sleepers. Here’s a quick overview of who’s most likely to want this bed.

Who Might Like The Amerisleep AS4?

  • Side sleepers, who need plenty of pressure relief around the shoulder and hip
  • Fans of a softer mattress – the AS4 makes our list of the best soft mattresses
  • People who like a balanced foam feel

Who Might Not Like The Amerisleep AS4?

  • Stomach sleepers, who need more support than this mattress offers
  • Larger back sleepers
  • Folks who like a firmer mattress

Save on the AS4 with Amerisleep mattress coupons.

Amerisleep AS4 Mattress Firmness and Feel

When you’re shopping for a new mattress, make sure to consider firmness and feel. These factors will have a major impact on whether a mattress is appropriately matched to your sleep position(s) and other sleep needs. Because of that, we’re kicking off this comprehensive review by taking a look at the Amerisleep AS4’s firmness and feel.

How Firm Is The Amerisleep AS4?

We ranked the Amerisleep AS4 around a 6 out of 10 on the firmness scale. The industry standard for medium firmness is 6.5/10, so this suggests the Amerisleep AS4 is softer than average.

Note that a person’s body weight will influence their perception of firmness. But in general, it’s safe to say that most people will find this mattress to be on the soft side.

Sleeping On The Amerisleep AS4 Mattress

While back sleeping on the Amerisleep AS4, we didn’t get quite enough spinal support (particularly lumbar support). Because this mattress is soft, our hips drop in and pull the spine out of alignment.

The Amerisleep AS4 really shines while side sleeping. The thick comfort layer of Bio-Pur foam allowed us to sink into the mattress for body contouring and pressure relief, and we felt almost no pressure around the shoulder and hip. This is one of the best mattresses for side sleepers.

Amerisleep AS4 - Side Sleeping

A mattress that’s great for side sleeping isn’t usually ideal for stomach sleeping, and that general rule holds true on the Amerisleep AS4. The soft nature of this mattress means it’s simply not supportive enough for stomach sleeping.

What Does The Amerisleep AS4 Feel Like?

Like all of the mattresses in the Amerisleep line, the Amerisleep AS4 has a balanced foam feel that is both pressure-relieving and responsive. It features one of the thickest comfort layers of all the Amerisleep mattresses (second only to the Amerisleep AS5), which lets sleepers sink into the bed and enjoy a great deal of pressure relief.

Average Weight Sleepers – 130lbs – 230lbs

Average-weight back sleepers who weigh less than 200 pounds should enjoy a balance of spinal support and pressure relief on the Amerisleep AS4, while folks who weigh more than that will probably feel the mattress isn’t supportive enough in this position. The Amerisleep AS4 is an excellent match for average-weight side sleepers; it lets you sink deeply into the mattress to enjoy plenty of pressure relief. This mattress is too soft for average-weight stomach sleepers, who won’t get adequate spinal support. Folks who spend all or a significant portion of the night on their stomachs will want to look for a dedicated mattress for stomach sleepers.

Heavyweight Sleepers – Over 230lbs

The Amerisleep AS4 is not supportive enough for heavyweight back sleepers, who will need to look for a firmer mattress. Most heavyweight side sleepers should feel great on the Amerisleep AS4, as the plush comfort layer relieves pressure around the shoulder and hip. (Note that folks who weigh more than 300 pounds might want to look for a dedicated mattress for heavy people.) The Amerisleep AS4 is much too soft to adequately support heavyweight stomach sleepers.

Lightweight Sleepers – Under 130lbs

Lightweight back sleepers should enjoy a mixture of pressure relief and spinal support on the Amerisleep AS4. Lightweight side sleepers will enjoy exceptional pressure relief around the shoulder and hip and should feel very comfortable on this mattress. The Amerisleep AS4 is probably too soft even for lightweight stomach sleepers.

30% Off
Amerisleep AS4
Amerisleep AS4
Amerisleep AS4

The Amerisleep AS4 is one of the brand's softest models and should be a great fit for side sleepers. Get 30% off the Amerisleep AS4 mattress by using code AS30

Amerisleep AS4 Mattress Construction

Now that you know what it’s like to sleep on top of the Amerisleep AS4, let’s peek under its cover! We’ll review each layer of this bed’s construction and assess how its materials affect performance.


The Amerisleep AS4 has a thin cover that’s fairly breathable and should allow for air to flow through the top of the mattress.

Comfort Layers

The Amerisleep AS4’s primary comfort layer is made from a whopping 4” of Bio-Pur foama plant-based, open-celled foam that’s simultaneously pressure-relieving and responsive. This foam is CertiPUR-US certified, which means it’s low in volatile organic compounds (VOCs) and is eco-friendlier than more conventional foams.

Amerisleep AS4 - Mattress Construction

Underneath the Bio-Pur foam layer, there’s a 1” HIVE Transition layer. This layer is zoned to create slight differences in firmness across the mattress. It’s a bit softer around the shoulders and hips (for extra pressure relief) and a touch firmer and more supportive around the head, back, and legs.

Support Layer

The Amerisleep AS4’s base layer is made from 7” of high-density Bio-Core foam, which provides structure and support to the entire mattress.

Mattress Height

The Amerisleep AS4 is 12” tall.

RELATED: Amerisleep AS2 vs AS3

Amerisleep AS4 Mattress Size Options and Price

To see the most up-to-date size and pricing information for the Amerisleep AS4 mattress, check out the chart below!

Size Dimensions Price
Twin 38″ x 74″ x 12″ $1449
Twin XL 38″ x 80″ x 12″ $1499
Full 54″ x 75″ x 12″ $1649
Queen 60″ x 80″ x 12″ $1799
King 76″ x 80″ x 12″ $2099
California King 72″ x 84″ x 12″ $2099
Split King 38″ x 80″ x 12″ (x2) $2998

Amerisleep AS4 Mattress Performance

Alright, you now have a clear sense of the Amerisleep AS4’s firmness, feel, and construction. Let’s finish off this review with a look at some key performance metrics. We put the Amerisleep AS4 through a range of tests to assess its temperature regulation, motion transfer, edge support, and more. Make sure to see our Amerisleep mattress comparisons to see how it stacks up against other brands.

Sleeping Hot Or Cold

The Amerisleep AS4 has two design elements that could help it sleep cooler than some all-foam mattresses: Its cover is breathable, and the Bio-Pur foam is open-celled to allow for more airflow. Still, this is an all-foam mattress, so it’s possible that it could trap some heat.

Motion Transfer

Even though the Amerisleep AS4 is fairly responsive, it still does a great job of minimizing motion transfer. The Bio-Pur foam absorbs motion and helps isolate it to one side of the mattress. This could be good news for folks who sleep with a partner.

Edge Support

We found the edge support on the Amerisleep AS4 to be okay but not great. If edge support is important to you, consider one of the firmer models in the Amerisleep mattress line (such as the AS1 or AS2).


This should be a very durable mattress, which is reflected in its longer-than-average warranty.


We did observe some off-gassing from the Amerisleep AS4. This chemical smell is normal and should dissipate within a few days.


This is not a noisy mattress at all, probably because it’s all-foam. We moved around on the mattress and changed positions, and we did not hear any real noise.


When people look for a mattress for sex, they usually want a bed that makes it easy to change positions. The Amerisleep AS4 is fairly responsive, so it could fit the bill. Partners shouldn’t feel stuck in this mattress.

RELATED: Best Mattress 

Overall Rating

Amerisleep AS4 Mattress
3.9 Overall
The Amerisleep AS4 is designed specifically for side sleepers and I can say that it worked very well when I slept in that position. I felt great pressure relief on my shoulders and hips. If you sleep primarily on your back or stomach, I would consider the firmer mattresses in the Amerisleep line.
Edge Support
Motion Transfer
Trial Period

Amerisleep Company Policies

If you’re interested in buying an Amerisleep AS4 mattress, it’s going to come with some fine print. We’ll explain the most important policies you should understand before purchasing.


Amerisleep offers a 20-year mattress warranty for the AS4 mattress. This means if you find something wrong with your mattress caused by manufacturing issues (i.e. tears in the cover), Amerisleep will repair or replace your mattress.

The first 10 years is a full replacement warranty, but the second 10 years are a prorated warranty, meaning you would have to cover some of the costs for replacement in those final 10 years.

Sleep Trial

Amerisleep offers a 100-night sleep trial period for the AS4 mattress. This allows you plenty of time to sleep on your AS4 mattress and figure out if it’s a good match for you. The trial period begins once your AS4 mattress arrives at your door.

Return Policy

If during that 100-night trial period you decide that the AS4 mattress isn’t a good fit for you, you can reach out to Amerisleep to initiate a return or exchange process. Should you choose to return your AS4 mattress during your trial period, you can receive a full refund.

Amerisleep does ask that customers wait 30 days before initiating a return or exchange as it can take some time to adjust and break in a mattress. If you insist on returning or replacing your mattress during the first 30 days, you will be charged a $99 fee.

How Does The Amerisleep AS4 Compare To Other Mattresses?

Now we’ll compare the Amerisleep AS4 mattress to the popular AS3 mattress from Amerisleep.

If you want to compare the AS4 to more mattresses, including those from other brands, you can check out our Amerisleep mattress comparisons.

Amerisleep AS4 vs AS3

The Amerisleep AS4 and the AS3 come from the same mattress brand, so they have many similarities. Firstly, they come with the same policies, including the warranty, trials period, and returns.

Additionally, these mattresses have fairly similar constructions. The AS3 and AS4 each feature a breathable cover, a 7” supportive high-density foam base layer, and a comfort layer in between made of plant-based, open-celled foam, although this foam layer is 1” thicker in the AS4. This results in the AS3 mattress having a slightly firmer feel than the AS4.

For those who prefer a softer mattress, the AS4 will be a better fit.

Amerisleep AS3 - construction and foam layers

When it comes to price, the AS4 mattress is slightly more expensive than the AS3, although the true value comes from determining which will be a better fit for you in the long-term.

Who Should Get The Amerisleep AS4? 

  • Those who want a softer mattress
  • Side sleepers who like ample cushioning

Who Should Get The Amerisleep AS3? 

  • Those who want a firmer mattress
  • Those looking to spend less money on a mattress
  • Heavier people who need a more supportive mattress

If you’re curious about the AS3, you can read our full AS3 mattress review to learn more about it.

Amerisleep AS4 Mattress FAQs

Now, we would like to answer some of the most frequently asked questions about the Amerisleep AS4 mattress.

How long will the Amerisleep AS4 mattress last?

The Amerisleep mattress should last for at least seven to ten years. This will depend on how heavy you are and how often you use the mattress.

Can you flip the Amerisleep AS4 mattress?

No, you cannot flip the Amerisleep AS4 mattress – it is only designed to lie with the Bio-Core foam on the bottom and Bio-Pur foam on top.

What if I don't like my Amerisleep AS4 mattress?

You have 100 nights to decide if the Amerisleep AS4 is a good match for you. If it’s not working for you, you can return it for a full refund.

Gravatar for Marten Carlson

Marten Carlson

Marten is Senior Editor at Mattress Clarity. He covers the mattress industry as well as sleep science news. He is specifically interested in the connection between sleep and overall health. Marten has written for media publications like Consequence of Sound and received a master’s degree in Film Studies from Emory University. He comes from Franklin, Indiana, and spends all the time he can writing, directing, and acting in films. He has directed genre short films and features. His newest film, Starlets, recently premiered at the River Town Film Festival in Clinton, NJ. He also stars in the upcoming thriller, Sour Bear. His next film, At The Hop, is a hot rod actioner with a horror twist.