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Mattress firmness indicates how the surface of a bed feels beneath the sleeper’s body. The cover and comfort (or topmost) layer of a mattress affects firmness to the greatest extent. At Tuck, we measure mattress firmness using a 1-to-10 scale, with 10 being the firmest and 1 being the least firm — although the vast majority of mattresses sold today fall between a 3 (‘Soft’) and an 8 (‘Firm’).
This page will discuss mattresses that rate as a 4 (‘Medium Soft’) and lower. Soft mattresses are generally most popular among side-sleepers due to improved spinal alignment and pressure relief, as well as lighter individuals who do not experience as much conforming on firmer models. However, softer mattresses have also been linked to certain disadvantages, such as high body heat retention, more off-gassing odor, and shorter overall lifespan.
This section will discuss various physiological factors — such as bodyweight and sleep position — that often indicate a sleeper will prefer a softer mattress. But first, a disclaimer: every sleeper is different, and this information applies to most — but not all — mattress owners. We highly recommend testing out a wide range of mattress firmnesses in order to determine your preferred rating before finalizing your purchase.
Let’s begin by talking about bodyweight. For the purposes of this page, the average sleeper weighs between 130 and 230 pounds; ‘below-average weight’ signifies anything less than 130 pounds, and ‘above-average weight’ applies to anything greater than 230 pounds. Bodyweight is one physical factor that generally correlates to firmness: people who weigh less tend to prefer softer mattresses, whereas heavier people often feel most comfortable on a firmer mattress.
Reasons for this correlation include conforming and pressure relief. Mattresses that are softer tend to sink more deeply beneath sleeper’s bodies; in contrast, firmer mattresses will not sink much (if at all) unless the sleeper weighs enough. For this reason, people in the below-average and average weight groups often feel most comfortable on softer mattresses because they can experience the full sinking effects, which can alleviate pressure points along the body, and less comfortable on firmer mattresses that do not sink as much or relieve pressure to the same extent. Alternatively, people in the above-average weight class may sink too deeply into a softer mattress, and this can lead to more pain and pressure. For this reason, heavier individuals tend to feel most comfortable on firmer mattresses. The table below includes the most popular firmness ratings for each of the three weight groups.
|Weight Group||Most Commonly Preferred Mattress Firmness|
|Below-average (Less than 130 Pounds)||4 (Medium Soft) and Lower|
|Average (130 to 230 Pounds)||5 (Medium) to 6 (Medium Firm)|
|Above-average (More than 230 Pounds)||7 (Firm) and Higher|
Sleep position also affects firmness preferences, since softer mattresses that conform more closely can also improve the sleeper’s spinal alignment. The back-sleeping position naturally aligns the spine on its own, and sleepers who choose this position may not need their mattress to aid spinal alignment. Side-sleepers, on the other hand, sleep in a position that creates an unnatural curvature in the spine. Those who sleep on their side require enhanced support in the neck, shoulders, lower back (lumbar), and hips in order to reduce pain and pressure. For this reason, side-sleepers often prefer Soft or Medium mattresses.
Most stomach-sleepers find soft mattresses somewhat uncomfortable. This is because they sink too deeply, causing them to turn their heads in order to avoid lying face-down on the sleep surface, and this can increase pain and pressure in the neck and shoulders. For heavier people who sleep on their stomachs, a softer mattress can be especially problematic because a high percentage of their weight may be located in their stomach. Stomach-sleepers in the below-average weight group, on the other hand, may feel comfortable on mattresses rated as Medium Soft because they provide some conforming without too much sinking.
The next table lists preferred firmness levels for different sleepers based on bodyweight and sleep position.
|Weight Group||Preferred Firmness for Most Side Sleepers||Preferred Firmness for Most Back Sleepers||Preferred Firmness for Most Stomach Sleepers|
|Below-average (Less than 130 pounds)||3 (Soft) to 5 (Medium)||4 (Medium Soft) to 6 (Medium Firm)||4 (Medium Soft) to 6 (Medium Firm)|
|Average (130 to 230 Pounds)||4 (Medium Soft) to 6 (Medium Firm)||5 (Medium) to 7 or 8 (Firm)||6 (Medium Firm) to 7 or 8 (Firm)|
|Above-average (More than 230 Pounds)||5 (Medium) to 6 (Medium Firm)||6 (Medium Firm) to 7 or 8 (Firm)||6 (Medium Firm) to 7 or 8 (Firm)|
Next, let’s discuss some of the different construction and performance factors shared by many mattresses that rate as a 4 or below on the firmness scale.
The table below evaluates Soft, Medium/Medium-Firm, and Firm mattresses based on these performance factors:
|Performance Factor||Soft (4 and Lower)||Medium to Medium Firm (5 to 6)||Firm (7 and Higher)|
|Longevity||Poor to Fair||Good||Good to Very Good|
|Average Price||High||Medium to High||Low to Medium|
|Conforming/Pressure Relief||Fair to Good||Very Good||Poor to Fair|
|Heat Retention||Poor to Fair||Good||Very Good|
|Off-gassing||Poor to Fair||Fair to Good||Good to Very Good|
|Sex||Poor to Fair||Very Good||Fair|
|Easy to Move||Poor to Fair||Fair to Good||Good to Very Good|
Now that you have determined that a softer mattress is most suitable for your sleep needs and preferences, let’s go over a few tips for buying the right model and maintaining it for years to come.
A softer mattress surface may be your best option if you belong to the below-average or average weight group, or you sleep on your side. If you prefer a firmer mattress, please visit our guide to the Best Firm Mattresses for details. You can also check out our Firmness Guide for more information.
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