Why weight changes firmness#
Firmness ratings are set against an average body, so the more you weigh, the further you compress a mattress and the softer it feels, while lighter sleepers experience the same bed as firmer. That's why weight is one of the most useful guides to the firmness you should buy. The general target for most people is medium-firm, which the evidence links to the best comfort, sleep quality and spinal alignment,1 with weight nudging you firmer or softer from there.
Mattress firmness by weight chart#
| Body weight | Side sleeper | Back sleeper | Front sleeper |
|---|---|---|---|
| Under 60 kg | Soft to medium | Medium | Medium to medium-firm |
| 60–90 kg | Medium to medium-soft | Medium to medium-firm | Medium-firm |
| 90–110 kg | Medium to medium-firm | Medium-firm | Medium-firm to firm |
| Over 110 kg | Medium-firm | Firm | Firm |
Treat this as a starting point, not a rule. It points you to the right zone; personal comfort and a home trial confirm the exact feel.
How to read the chart#
- Lighter sleepers need softer surfaces to compress the comfort layer enough for pressure relief, especially on the side.
- Average-weight sleepers sit closest to standard firmness ratings, so position matters more than weight.
- Heavier sleepers need firmer support to stop the hips sinking and the spine sagging, and benefit from robust cores that resist early softening.2
Position fine-tunes it#
Within your weight band, your sleeping position shifts the ideal: side sleepers go a notch softer (to cushion the shoulder and hip), front sleepers a notch firmer (to keep the hips lifted). For the full breakdown, see our sleeping position guide and body weight guide.
It still comes down to fit#
Charts narrow the shortlist, but comfort ultimately depends on the interaction between sleeper and surface, which is why preference and a trial matter.3
Browse by firmness and type or take our quiz for a personalised recommendation.
Kilograms to stones#
The chart above uses kilograms because that is what the research uses. Most UK readers think in stones, so:
| Kilograms | Stones and pounds | Chart band |
|---|---|---|
| Under 60 kg | Under 9 st 6 lb | Lighter |
| 60–90 kg | 9 st 6 lb – 14 st 2 lb | Average |
| 90–110 kg | 14 st 2 lb – 17 st 5 lb | Heavier |
| Over 110 kg | Over 17 st 5 lb | Much heavier |
Our catalogue by firmness#
Once the chart has given you a firmness band, these are the mattresses we have scored in each. Prices are for a double at the time of writing (September 2026), using the sale price where the brand runs one; live prices are on each review page.
| Firmness | Mattresses we have scored | Ranked list |
|---|---|---|
| Soft | Tencel 1000 (£339, pocket sprung), Reverso Memory (£329, foam) | Best soft |
| Medium-soft | Luxe Nova Hybrid (£449, hybrid), Tempure Velure Pillow-Top (£449, foam) | Best for side sleepers |
| Medium | Emma Original (£469, foam), Emma NextGen Premium Plus (£679, foam), Luxe Velour Hybrid (£399, hybrid), LuxeTherm Hybrid (£337, hybrid), LuxeOrganic Hybrid Latex (£471, latex), Pocket Reflex 1000 (£399, sprung), plus The Foam People range from £109 | Best hybrid, Best memory foam |
| Medium-firm | Emma Original Pro (£699, hybrid), Emma Original Elite (£999, hybrid), Luxe-Latex Natural Pillow Top 5000 (£674, latex) | Best for back pain |
| Firm | LuxeErgo 3400 Hybrid (£464, hybrid), Imperial 2000 (£449, sprung), Majestic 11000 (£318, foam), Majestic 9000 (£273, foam), Luxe OrthoSupport9 (£410, foam), Comfort Ortho Firm (£157, foam) | Best firm |
Depth matters more as weight rises#
The chart tells you the firmness; it does not tell you the build, and for heavier sleepers the build matters at least as much. A firm 18cm foam mattress and a firm 31cm hybrid are both "firm", but a sleeper over 100kg will compress the thin one through to the base and find it both harder and less supportive than the label suggests. Rules of thumb by band:
- Under 60 kg: depth is not a constraint; 20cm and above is fine. Focus on a comfort layer soft enough to actually compress under you.
- 60–90 kg: 23 to 25cm is the sensible floor for nightly adult use. Almost everything in our catalogue qualifies.
- 90–110 kg: 25cm and above, and favour pocket springs or high-density foam in the core. Cheap low-density foam softens fastest under heavier loads.2
- Over 110 kg: 28cm and above, a hybrid or reinforced sprung core, and a warranty of 10 years. The LuxeErgo 3400 (31cm) and Emma Original Elite (28cm, 9.3 support) are the two we would start with. See our guide for heavier sleepers.
Couples in different bands#
If you and your partner sit in different weight bands, the chart gives two answers. The compromise that works most often is to buy for the heavier partner's support band and the lighter partner's comfort: a medium-firm hybrid with a generous comfort layer, so the core holds the heavier sleeper while the surface still gives for the lighter one. If you are two bands or more apart, two single mattresses on a zip-and-link or split base is the honest solution. Our couples guide goes into the options.
Frequently asked questions#
What firmness mattress should I get for my weight?#
Start at medium-firm, which the evidence favours for most people,1 then go a notch softer if you are under about 60kg (9.5 stone) or a side sleeper, and a notch firmer if you are over about 90kg (14 stone) or a front sleeper. The chart above combines the two.
Does a heavier person need a firmer mattress?#
Usually, because they compress any mattress further, so a medium reads as medium-soft to them. Just as important is a deeper, denser build that resists sagging. A firm but thin mattress is not the answer.
What mattress firmness is best for a 100 kg person?#
Medium-firm for side and back sleepers, firm for front sleepers, in a build at least 25cm deep with a pocket-spring or high-density foam core. Look at the medium-firm and firm rows in the catalogue table above.
Is a soft mattress OK for a lightweight person?#
Often it is the right choice. Lighter sleepers do not compress a firm mattress enough to get pressure relief, so soft to medium (especially for side sleepers) is where they usually end up. See our best soft mattress list.
Does mattress firmness change over time?#
All mattresses soften a little in the first weeks and then stabilise; low-density foam keeps softening.2 Heavier sleepers accelerate this, which is another reason to favour density and depth over the firmness label alone.
References#
- Caggiari G, Talesa GR, Toro G, Jannelli E, Monteleone G, Puddu L. What type of mattress should be chosen to avoid back pain and improve sleep quality? Review of the literature. Journal of Orthopaedics and Traumatology. 2021;22:51. doi:10.1186/s10195-021-00616-5
- Vlaović Z, Klarić N, Domljan D. Investigating the Impact of Long-Term Use on Mattress Firmness and Sleep Quality: Preliminary Results. Applied Sciences. 2024;14(21):10016. doi:10.3390/app142110016
- Robbins R, Quan SF, Barger LK, et al. Validation of the Boston Mattress Satisfaction Questionnaire. Frontiers in Sleep. 2025;4:1509420. doi:10.3389/frsle.2025.1509420
