The UK firmness rating problem#
There is no standardised firmness rating system in the UK mattress market. Emma's "medium" and Simba's "medium" and Hypnos's "medium" may feel meaningfully different from each other. European brands use H1–H5 designations (H1 being softest); UK brands typically use soft/medium-soft/medium/medium-firm/firm labels. These are internally consistent within a brand but not comparable across brands. Always use trial periods to assess actual feel rather than relying on firmness labels alone.
The typical UK firmness scale#
| Label | Who it suits | European equivalent |
|---|---|---|
| Soft | Light side sleepers (under 9 stone); those with pressure point pain | H1–H2 |
| Medium soft | Side sleepers of average weight; lighter combination sleepers | H2 |
| Medium | The most versatile — suits most average-weight side, back and combination sleepers | H3 |
| Medium firm | Back sleepers; heavier side sleepers; those who find medium too soft | H3–H4 |
| Firm | Stomach sleepers; very heavy sleepers; those requiring maximum support | H4–H5 |
| Orthopaedic/extra firm | Heavy sleepers requiring maximum support; post-surgery specific recommendations | H5 |
How body weight modifies firmness perception#
The same mattress feels different to a 8-stone person and a 17-stone person. Heavier sleepers compress comfort layers more deeply, making any given firmness feel softer than it does to a lighter person. As a rule of thumb: if you're above 14 stone (90 kg), consider one step firmer than the standard recommendation for your sleep position. If you're below 9 stone (57 kg), consider one step softer.
Firmness and sleep position: the decision matrix#
Combining your sleep position and weight gives you a starting firmness to look for:
- Light side sleeper (under 9 st): Soft to medium-soft
- Average side sleeper (9–14 st): Medium-soft to medium
- Heavy side sleeper (over 14 st): Medium to medium-firm
- Light back sleeper: Medium
- Average back sleeper: Medium to medium-firm
- Heavy back sleeper: Medium-firm to firm
- Stomach sleeper (any weight): Medium-firm to firm
- Combination sleeper: Medium (most versatile)
What "orthopaedic" actually means#
In the UK, "orthopaedic" is a marketing term — not a medically certified designation. Any mattress brand can call a mattress "orthopaedic." It typically indicates a firmer mattress, but there's no regulatory body that certifies what qualifies. Don't pay a premium for the "orthopaedic" label alone. Assess the firmness, construction and materials independently.
The role of trial periods#
Given that firmness perception is so individual and brand labels are inconsistent, trial periods are essential. Use the trial to assess how you feel on waking — not how comfortable the mattress feels when you first lie on it. A mattress that feels luxuriously soft in week one may feel too soft by week eight as your body provides more data. The 8-week mark is often when sleepers make a more reliable judgement about firmness suitability.