Choose Your Mattress Firmness by Sleeping Position

A guide to what side sleepers, back sleepers, and stomach sleepers should look for in terms of mattress firmness.

By Sheryl Grassie

Feb 21st, 2023

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Among the various considerations when purchasing a mattress, firmness ranks at the top of the list along with material and price. For most people, firmness equates to how comfortable the mattress is for sleeping. Some people prefer a soft mattress, others a very firm mattress, but the majority of us, roughly 80%, prefer a medium-firm mattress.

When it comes to firmness preference, the experience of what is comfortable is as individual as we are. There are, however, guidelines on firmness depending on the sleep position you enjoy, and these guidelines can save you a lot of work, especially if you are buying a mattress online and can’t try it out beforehand.

Although most online companies have sleep trials to test out your bed, you may want a pretty good idea before ordering. Finding your best firmness, and thus your most comfortable mattress, is the goal, so let’s better understand mattress firmness and what will work best for your sleep position.

What Is Mattress Firmness?

Firmness describes the spring back factor and the sink factor of a mattress in terms of feel. Sleeping on a wood pallet would be an example of a very firm sleep surface and is actually common in some countries. A very soft sleep surface would be like sleeping on feathers, like a large down comforter. With a firm mattress your body rests more on the surface, with a soft mattress you sink deeper and meld with the mattress.

Related: Best pillow top mattresses

You can give some thought to which feeling you like best. Memory foam mattresses were well-known for their soft, sink-into-the-mattress feeling which appeals to some and not to others. Some people find a soft mattress claustrophobic and prefer a firmer surface. Again, it is all about what is comfortable for you.

Related: Mattress firmness guide

Does Mattress Firmness Describe Support?

In a word, no. Firmness and support are two different things. Mattresses at any level of firmness can offer support, but in part, that depends on your sleeping position. It also depends on what you find comfortable and other factors like your weight. However, given that so many mattress choices are online, purchases that you can’t try ahead, it warrants knowing ahead what you will most likely find both comfortable and supportive.

Firmness by Sleeping Position

Start by knowing your sleep position. Although there are subcategories with sleep positions, they all fall into one of three primary categories; side sleeper (most common position), back sleeper (closely tied for 2nd most common), or stomach sleeper ( 2nd most common position), and of course, some of us are combination sleepers who change positions over the course of the night. If you’re searching for a good mattress as a combination sleeper, choose your most predominant position, the one you find yourself sleeping in the most.

In addition to sleep position, to find the right mattress you will need to throw in some additional factors like weight, temperature preference, and motion transfer. Each of these additional factors lends themselves to meeting that goal of knowing how to pick your most comfortable mattress.

Side Sleeper

A side sleeper is a person who lies on either side for the majority of the night. This is the most common sleep position, probably because it takes the strain off back and hips, and estimates are that somewhere between a half and three quarters of us sleep on our sides. This is a position favored by women, and there is support for this being the best position for reducing heartburn and helping with heart circulation, especially if you sleep on your left side.

Sleep experts also recommend side sleeping for pregnancy because it keeps circulation moving, supports good spinal alignment, and promotes more optimal nerve functioning. Side sleeping also helps to support the body’s natural detoxification process.

Related: Best mattress for side sleepers

Side sleepers do best with a mattress that isn’t too soft and isn’t too hard, the goldilocks version of something in the middle, something that is “just right.” If the mattress is too soft, you won’t get the support you need for your shoulders and hips and they will sink too low in the mattress. But you do need a mattress with plenty of give to support those sharp curves, so you don’t want one that is too firm either.

A medium-soft mattress works best for side sleepers, although some can comfortably go into a med-firm if they are heavier. Latex and memory foam mattresses are both good choices that offer support for those deep curves. Try a mattress in the 3 to 7 range of firmness.

Back Sleepers

Back sleepers are a smaller percentage of the population with only about 10% to 15% of people sleeping on their backs. For many people it is not enough support, especially for the lower back. It can also encourage snoring and problems like sleep apnea. In the cosmetic department is it favored, however, as it lets your facial skin breath. Also having no contact with a pillow your face incurs less wrinkles and oils are not trapped that can cause acne.

A medium-firm mattress is suggested for back sleepers. Choose 5 to 8 firmness range, a good choice is pocketed coils with a latex top.

Related: Best mattress for back sleepers

Stomach Sleepers

Stomach sleepers make up about 16% of the sleeping population and generally need a somewhat firmer mattress. If the mattress is too soft, your abdomen will sink and throw your spine out of alignment. There is also concern that stomach sleeping puts pressure on internal organs and does not give adequate support to the neck and spine. This can result in back and neck pain. A bonus to stomach sleeping, is the lack of snoring.

For stomach sleepers, a medium to firm mattress works best. Choose a firmness rating between 6 and 9 (ex. airweave mattress) for your most comfortable sleep.

The chart below, shows in red, the range of firmness for each sleeping position.

Related: Best mattress for stomach sleepers

Other Variables

There are a few other variables that need factoring in when you consider your choice of firmness. Weight, temperature preferences, and motion transfer concerns. Let’s look briefly at each one.


The heavier you are, the more you will sink into your mattress. This means that a very soft mattress is not a good choice if you are at the higher end of the weight spectrum. Weight and firmness have an equivalent relationship, meaning, that as your weight goes up, so should the firmness of your mattress. That means for example, that if you are a side sleeper, and you are over 200 lbs., you would want a mattress in the higher end of the med-firm range. See the chart below for more weight ranges.

Firmness Notes Sleep Position Weight
1 = Very Soft Rare and hard to find, maximum sink Side Sleepers Under 130 lbs.
2 – 3 = Soft Quite soft, body will sink deep Side Sleepers Under 130 lbs.

to 225 lbs.

4 – 6 = Medium Some give with a firm underlay Side, Back and Stomach Sleepers 130 lbs. to 225 lbs.
7 – 9 = Firm Very little sink or give Side, Back and Stomach Sleepers 225 lbs. and over
10 = Extra Firm Like sleeping on a wooden pallet Stomach Sleepers 225 lbs. and over


Some types of beds run hot and some are designed to be cooling. Memory foam, which is very soft, can run hot. If you don’t like to sleep hot, you may want to move up from a softer bed to one that is a little firmer or find a gel-infused memory foam for cooler sleeping.

Motion Transfer

Mattresses can move in relation to movement, but some quite a lot and others almost not at all. If you sleep with a partner who tosses and turns, have animals that jump on and off the bed, or children that are climbing in and out throughout the night, you might want a mattress with less motion transfer. That would point towards memory foam or pocketed coils. If you are a stomach sleeper and motion transfer is an issue, look at pocketed coils with a minimal top, memory foam will likely be too soft.

Related: Best mattress for couples


Firmness is a matter of preference, but your sleep position will generally dictate the level of firmness you find most comfortable. Firmness is not the same as support and all levels of firmness can be supportive.

Most sleep positions do well in the middle with side sleepers ranging softer and stomach sleepers a bit firmer. Back sleepers do well in the medium to firm range. Add in other considerations like weight and if you have issues with bed motion or sleeping too hot at night, and then decide.

If you buy a mattress online there are many companies with sleep trials so you can test out your choice and return it if it isn’t the right firmness. This way, you can find the best mattress firmness for you.