Mattress firmness quiz
Three questions, and the arithmetic behind the answer shown in full.
Firmness is what buyers get wrong most often, and the reason is that a rating describes how a mattress responds to a standard load. You are not a standard load.
How the answer is worked out
No black box. The quiz applies three adjustments in order.
| You sleep | Start at | Because |
|---|---|---|
| Side | 4 to 6 | Shoulder and hip must sink for the spine to stay straight |
| Back | 6 to 8 | The lumbar hollow needs filling without the hips dropping |
| Front | 7 to 9 | The hips must be held up or the lower back over-extends |
| Combination | 6 to 7 | A middle rating beats optimising for one position |
Then weight. One step softer under about 11 stone, one step firmer over about 16. Firmness ratings are calibrated for roughly 10 to 15 stone, so outside that band the number means something different.
Then symptoms. Lower back ache on waking that eases as you move usually means too soft. Hip or shoulder pain when side sleeping usually means too firm.
What this cannot tell you
There is no industry standard behind the firmness scale. Each manufacturer sets its own numbers, so a 7 from one brand is not necessarily a 7 from another. The range is a shortlist filter, not a specification.
Firmness is not support. Firmness is how the surface feels immediately; support is whether your spine stays in a reasonable position all night. A firm mattress with few springs is firm by barely compressing, which is not the same thing.
Your base changes the answer. A platform top divan firms a mattress; sprung slats soften it. The same mattress on two bases is two different beds.
Two people need two answers. If you share with someone much heavier or lighter, one surface cannot be right for both, and dual firmness or zip and link is the structural fix. It works properly from king width upward, because you need to be clear of the transition zone down the middle.
What to do with the number
Use it to shortlist, then buy with a trial. A comfort exchange beats a refund, because it lets you correct the firmness rather than start the search again.
Give it a fortnight. A new mattress feels different from the one you have adapted to, and your body takes that long to recalibrate. This is why trials have minimum periods of around 21 to 30 nights.
Ask for the construction too, either spring count in your size or foam density, because a firmness number without either tells you very little about how long it will last.
Related reading
Understand the scale
Buy by firmness
How this site works
Nothing here is paid for by a brand. No manufacturer has copy approval, a preview, or the ability to change a score, and where a link earns a commission that never changes a ranking.
Where a brand does not publish a specification, that is stated rather than estimated, because an absent number is itself information. The corrections log and the products I will not recommend page are both public.