Expert Reviews of the Best Soft Mattresses for Pressure Relief

What makes a mattress truly soft, and when does soft become too soft?

Soft mattresses fall between 3 and 5 on the standard 10-point firmness scale. At that range, the comfort layers are deep enough that your shoulders and hips sink below the plane of the mattress surface, reducing contact pressure on bony prominences. For side sleepers under roughly 180 lb, that sinkage is exactly what the spine needs: hips drop into the mattress, the lumbar curve is preserved, and the shoulder joint stops grinding into a rigid surface.

The failure mode of soft mattresses is the same as their selling point. If the sinkage goes too deep, particularly at the hips, which are heavier than the shoulders, the lumbar spine tips into a slight forward tilt, and within a few hours that tension accumulates. This is why foam density and support core quality matter more than the feel of the comfort layer alone. A well-engineered soft mattress uses a plush comfort layer above a denser, zoned support core. A poorly engineered one is just a thick layer of low-density foam with no structure underneath.

Three sleeper profiles consistently benefit from a soft mattress:

• Side sleepers under 180 lb, the most common audience. Lighter frames do not compress soft comfort layers as deep as heavier ones, so sinkage stays in the ideal 1.5 to 2.5 inch range.
• Pressure-sensitive sleepers, including those with hip bursitis or fibromyalgia, where surface contact is painful. Soft foam reduces peak pressure at the hip and shoulder by spreading load over a wider area.
• Sleepers who run cold, soft, deep foam wraps more of the body surface, which retains more heat. If you already sleep cold, that is a benefit. If you sleep hot, factor in the mattress's ventilation design.

Soft mattress comparison: key specs at a glance

Mattress	Type	Firmness	Queen price	Trial	Warranty
Saatva Classic (Plush Soft)	Innerspring hybrid	Plush Soft ~3/10	~$1,395 (promo)	365 nights	Lifetime
Amerisleep AS3	All-foam (Bio-Pur)	Medium 5/10	From $1,049	100 nights	20 years
Amerisleep AS5 Hybrid	Hybrid (foam + coils)	Soft 3/10	From $2,099	100 nights	20 years
Puffy Original	All-foam in-a-box	Medium ~6/10	~$1,499 (promo)	101 nights	Lifetime

Soft, plush, or ultra-plush: picking the right firmness level

Soft mattresses are not a single point on the scale. Most manufacturers span a range from about 4/10 (often called "plush") down to 2.5/10 (true ultra-plush). Here is a practical way to map your profile to the right firmness:

• Under 130 lb, strict side sleeper: A true soft or ultra-plush (3 to 4/10) lets your hip sink enough for the spine to settle without pressure. The Saatva Classic Plush Soft and the Amerisleep AS5 Hybrid are the strongest picks in this range.
• 130 to 180 lb, side or combination sleeper: Medium (4.5 to 5.5/10) gives a plush feel without bottoming out. The Amerisleep AS3 sits exactly in this window and handles back sleeping during the night without the lumbar dip that pure-plush mattresses cause.
• Over 180 lb, side sleeper: The comfort layer compresses further under heavier body weight. A mattress labeled "medium" may feel soft in practice. Going too soft risks sinking past the comfort layer into the support core. A hybrid with reinforced coils, like the Saatva Classic, handles this better than a pure-soft all-foam.

Pressure relief: the metric that matters most

Pressure relief is measured at the hip, shoulder, and knee in standardized testing. The Saatva Classic Plush Soft achieves pressure relief through its Euro pillow-top layer, which adds deep cushioning, while the dual-coil core underneath keeps the support structure from collapsing. The result is a softer feel with more responsiveness than slow-recovery foam, and cooler sleeping, which matters if you tend to overheat on all-foam beds.

The Amerisleep AS3 scores at the top of independent lab tests for pressure relief. That performance comes from the Bio-Pur layer, which has a more open cell structure than traditional memory foam, letting it conform quickly without trapping heat in the same way. For a medium feel with active lumbar zoning, it remains the top all-foam option.

Will a soft mattress hold up over time?

Soft mattresses compress faster than firm ones under equivalent weight and usage, because the comfort layers are under greater constant stress. The two things that determine long-term durability in a soft mattress are foam density and support core quality.

The Saatva Classic's dual-coil system is inherently more durable than single-layer foam. The tempered steel coils resist permanent deformation, and the lumbar zone reinforcement prevents the center third from compressing faster than the edges, which is the classic failure pattern of lower-cost innerspring mattresses. The lifetime warranty reflects that confidence.

The Amerisleep AS3's Bio-Pur foam uses a 4 PCF density comfort layer, which is at the higher end for all-foam beds in this price range. The Bio-Core high-density base foam (1.5 PCF, 35 ILD) provides a stable foundation. Amerisleep covers sagging greater than 1.5 inches under the 20-year warranty.

Frequently asked questions

Who should sleep on a soft mattress?

Side sleepers under roughly 180 lb benefit most. Soft comfort layers allow the hip and shoulder to sink below the mattress surface, reducing contact pressure and keeping the spine in lateral alignment. Back sleepers under 130 lb can also do well on a soft mattress. Stomach sleepers and anyone over 230 lb should generally avoid pure-soft firmnesses to prevent lumbar hyperextension and premature sagging.

Is soft or medium better for side sleepers?

Medium-to-soft (4 to 5.5/10) is the most practical choice for most side sleepers across a range of body weights. Pure soft (3/10 and below) works best for very lightweight sleepers. A medium with strong zoning, like the Amerisleep AS3, outperforms a pure-soft mattress for most side sleepers because it cushions the pressure points while maintaining lumbar support. The Saatva Classic Plush Soft hits true softness while the dual-coil core provides structural integrity.

Can a soft mattress cause back pain?

Yes, if it is too soft for your body weight and sleep position. When the hips sink below the spine's natural alignment, the lumbar ligaments and intervertebral discs sustain low-grade strain over several hours. A well-structured soft mattress with a dense support core prevents this. If you wake with lower back stiffness that eases after 30 minutes of movement, the mattress sinkage is likely too deep for your profile.

How do I know if a mattress is too soft?

Four signs: (1) you feel like you are sleeping in a hammock, hips lower than shoulders. (2) Lower back stiffness that takes time to ease after waking. (3) Difficulty changing positions during the night. (4) You can see a permanent body impression in the mattress even before the warranty threshold. If any apply, size up in firmness or move to a hybrid where the coil core provides more consistent rebound.