How to Choose Mattress Firmness
Firmness is about feel and support, not quality — the 'right' firmness depends mostly on your sleeping position and body weight. Here is how to match them.
The firmness scale
Most UK retailers use a soft-to-firm scale. As a rough guide:
- Soft (1–3): deep cushioning, good for lighter people and side sleepers.
- Medium (4–6): the most popular all-round range; balances support and comfort.
- Firm (7–8): minimal sink, good for back and front sleepers and heavier bodies.
- Extra firm (9–10): very supportive, specialist or clinical use.
There is no industry-wide standard, so one brand's "medium" can differ from another's — treat firmness ratings as a guide, not a guarantee.
Match firmness to how you sleep
| Sleep position | Suggested firmness | Why |
|---|---|---|
| Side | Soft–Medium | Lets shoulders and hips sink so the spine stays level |
| Back | Medium–Firm | Supports the lower back while cushioning shoulders |
| Front (stomach) | Firm | Stops the hips sinking and over-arching the back |
| Combination | Medium | A safe middle ground for people who move around |
Adjust for body weight: heavier sleepers generally find a given mattress feels softer, so may size up a level of firmness; lighter sleepers often prefer a level softer to get enough pressure relief.
Frequently asked questions
What firmness of mattress is best for back pain?
Research and clinical guidance generally favour a medium-firm mattress for lower back pain — firm enough to keep the spine aligned, with enough give to cushion pressure points. The best choice still depends on your sleeping position and weight.
Is a firmer mattress better for you?
Not automatically. A mattress that is too firm can create pressure on the shoulders and hips, especially for side sleepers. The goal is neutral spinal alignment, which for many people means medium or medium-firm rather than the firmest option.
Can you soften a mattress that is too firm?
Yes, to a degree. A mattress topper can add cushioning, and many mattresses soften slightly over the first few weeks of use as the comfort layers settle. If it is still uncomfortable, use the trial or returns period.