Choose mattress firmness by sleeping position and body weight: side sleepers generally need medium to medium-soft, back sleepers medium to medium-firm, and front sleepers firm. Heavier sleepers need firmer support to avoid sinking; lighter sleepers need softer surfaces to get any contouring at all.
Table of contents
- The UK firmness scale explained
- Firmness by sleeping position
- Firmness by body weight
- Firmness for back pain
- Frequently asked questions
The UK firmness scale explained
| Rating | Feel | Typically suits |
|---|---|---|
| Soft | Deep sink, close contouring | Lighter side sleepers |
| Medium | Balanced give with support | Most side and combination sleepers |
| Medium-firm | Supportive with slight give | Back sleepers, average-to-heavier builds |
| Firm | Minimal sink, flat support | Front sleepers, heavier builds, some back-pain sufferers |
Firmness ratings are not standardised between manufacturers — one brand's medium is another's medium-firm. Treat them as a guide, not a specification.
Firmness by sleeping position
Side sleepers need the mattress to yield at the shoulder and hip so the spine stays straight — medium to medium-soft usually. Too firm and pressure builds at those two points.
Back sleepers need the lower back supported without the hips dropping — medium to medium-firm.
Front sleepers need to stop the hips sinking, which arches the lower back — firm is almost always right.
Combination sleepers do best on medium, which compromises acceptably across positions.
Firmness by body weight
Body weight changes how any mattress feels. Under roughly 60kg, firm mattresses feel unyieldingly hard because there is not enough load to compress the comfort layers. Over roughly 90kg, softer mattresses compress too far and lose support. Two people of very different weights sharing a bed are the strongest argument for pocket springs, which respond independently — see pocket sprung vs memory foam.
Firmness for back pain
The old advice that back pain always needs the firmest possible mattress is outdated — research generally points to medium-firm as the better starting point for most people, because a too-firm surface leaves the lumbar curve unsupported. That said, back pain has many causes; if yours is persistent or severe, speak to a GP or physiotherapist rather than relying on a mattress change alone.
Pocket sprung, orthopaedic, pillow top and memory-topped open coil — UK made, all sizes, from £149 with free delivery.
Browse mattresses →Frequently asked questions
What firmness is best for side sleepers?
Medium to medium-soft, so the shoulder and hip can sink enough to keep the spine level.
Is a firm mattress better for back pain?
Not necessarily — medium-firm suits most people better than very firm. Persistent pain warrants medical advice.
Does body weight change which firmness I need?
Yes — lighter sleepers generally need softer, heavier sleepers firmer, for the same perceived support.
Are firmness ratings standardised in the UK?
No. They vary by manufacturer, so compare within a brand rather than across brands.
