Choosing mattress firmness by sleep position

Firmness is subjective, but sleep position narrows the range. Side sleepers usually want softer surfaces; stomach sleepers usually want firmer ones.

Side sleepers

Softer to medium surfaces let the shoulder and hip settle so the spine stays level. Too firm and pressure builds at those two points.

Medium to medium-firm generally keeps the lower back supported while still cushioning the shoulders.

Firmer surfaces stop the hips from sinking below the shoulders, which is the main cause of lower-back discomfort in this position.

A responsive medium-firm build makes it easier to change position without feeling stuck.

Last reviewed August 11, 2026. See our methodology and mattress reviews.