How to Choose Mattress Firmness: A Sleep Position Guide

What firmness actually means

Mattress firmness is measured on a 1-10 scale, where 1 is the softest (think marshmallow) and 10 is the firmest (think floor). Most adults sleep best on a 5-7, with side sleepers leaning softer and back/stomach sleepers leaning firmer.

Firmness is different from support. A mattress can feel soft on top while still keeping your spine aligned — that's the goal of a quality hybrid build.

Best firmness by sleep position

Side sleepers (4-6): A medium-soft to medium feel relieves pressure on your shoulder and hip, the two contact points that take the most weight on your side.

Back sleepers (6-7): Medium-firm keeps your lumbar spine supported without letting your hips sink too far.

Stomach sleepers (7-8): Firmer surfaces prevent your hips from collapsing into the mattress, which is the main cause of stomach-sleeper back pain.

Combination sleepers (5-7): Medium is the safest pick because it works across positions without pressure points.

Body weight matters too

Lighter sleepers (under 130 lbs) tend to feel mattresses 1-2 points firmer than average. If a 'medium' (5-6) sounds right, go a step softer.

Heavier sleepers (over 230 lbs) compress mattresses more, so they often need 1-2 points firmer than average for proper support.

Frequently asked questions

Is a firmer mattress better for back pain?

Not always. Most people with back pain do best on a medium-firm mattress (6-7) that supports the spine without forcing it into a flat position. Too-firm mattresses can actually worsen pain by removing the natural curve of your lumbar spine.

Can I make a firm mattress softer?

A mattress topper can soften the feel by 1-2 levels, but it can't fix a mattress that's wrong for your body. If you're more than 2 levels off, return and exchange — that's what the 100-night trial is for.