Mattress firmness is rated on a 1 to 10 feel scale, where 1 is very soft and 10 is very firm. Most sleepers are comfortable between 5 and 7. Your ideal number depends on two things: your sleep position and your body weight. Firmness controls how a bed feels, not how well it supports your spine, and the two are often confused.
Firmness is the most talked about and least standardized part of buying a mattress. One brand’s “medium” is another’s “firm,” and there is no legal definition. Use the scale below as a common language, then adjust for your body.
| Rating | Feel | Best for |
|---|---|---|
| 2 to 3 | Very soft | Lightweight side sleepers who want a deep hug |
| 4 to 5 | Soft to medium | Side sleepers, lighter bodies |
| 6 to 7 | Medium to medium-firm | Back sleepers, combination sleepers, most people |
| 8 to 9 | Firm | Stomach sleepers, heavier bodies, those who want support on top |
Side sleepers need the surface to give at the shoulder and hip, so aim for soft to medium (around 4 to 6). Too firm and you get pressure points; see our side sleeper picks. Back sleepers want the spine held in a neutral line, which usually means medium-firm (6 to 7). Stomach sleepers should go firmer (7 to 9) so the hips do not sink and strain the lower back.
Body weight changes how firm a mattress feels because heavier bodies compress the comfort layers more. As a rule of thumb, lighter sleepers under about 130 pounds feel a bed firmer than average and often prefer a softer rating, average-weight sleepers can follow the position guidance above, and heavier sleepers over about 230 pounds usually want a firmer, more supportive build to avoid sinking too far. If you have back pain, our back pain guide goes deeper.
Many people believe a firm mattress is always better for the back. It is not. A mattress that is too firm can create pressure at the shoulders and hips and push the spine out of line, especially for side sleepers. Support comes from the mattress core doing its job; firmness is just the feel of the top layers. You want the firmness that keeps your spine neutral in your sleeping position, which is often medium-firm rather than rock hard.
Once you know your target firmness, choose a construction that delivers it in our mattress types guide, or start from the top with the full mattress buying guide.
Most research and owner feedback point to medium-firm, around 6 to 7, for general back pain, because it supports the spine without creating pressure points. The right number still varies with your weight and sleep position.
To a degree. A firm mattress topper can soften a too-hard bed, and a supportive board or a low-loft topper can firm up one that is too soft. These are adjustments, not fixes for a mattress that is genuinely wrong for you.
Yes. New mattresses often feel slightly firm and soften a little over the first few weeks as materials settle. Excessive softening or body impressions later on is a sign of wear, not break-in.