Home
Guides
Guide

Mattress Firmness: How to Choose When the Labels Aren't Standard

bed.chat 2026-10-28

Mattress firmness labels are not a standard you can compare across brands. Which? says many brands define firmness however they want, outside the official standard or with their own firmness scale, so you can't rely on those labels to compare firmness between brands.

Even the testers' scales run in different directions

Which? rates firmness from 1 to 10, where 1 is the firmest and 10 is the softest. Consumer Reports rates firmness from 1 (extremely soft) to 10 (extremely firm), measured against an industry standard. The 2003 Lancet randomised trial (Kovacs et al.) used a scale developed by the European Committee for Standardisation, which runs from 1.0 (firmest) to 10.0 (softest).

Which? says it measures firmness with a specially designed machine based on the mattress standard.

Firmness is partly personal

Which? says firmness comes down to personal preference. In its test notes, Which? says softness is subjective and depends on your preference, any health conditions, the state of your current mattress and the type you buy.

The Polyurethane Foam Association, the foam industry's own trade association, says firmness is independent of foam density, and that high-density foams can be soft and low-density foams can be firm.

Starting points: your weight and how you sleep

Heavier than average: Which? says you generally need a denser or firmer mattress, with a higher density of foam or springs.
Petite or lighter than average: Which? suggests a mattress that lets your body sink in while supporting the curve of your spine.
Front and back sleepers: CHOICE says that if you sleep on your stomach a firm mattress will keep your spine aligned, and if you sleep on your back a medium mattress will support your spine, back and neck.

Firm is not the same as supportive

Which? says body support depends more on how well a mattress adapts to your body shape and sleeping position than on how firm it feels. Which? says a mattress that is too firm can put pressure on your shoulders and hips, while one that is too soft can take your spine out of its best position. Which? also says a firmer mattress is not necessarily more supportive, since it has tested both foam and spring mattresses that give excellent body support.

CHOICE puts it in terms of comfort: a mattress that is too soft takes more effort to move on, and one that is too firm feels uncomfortable on your hips and shoulders.

Your bed base changes the feel

CHOICE suggests making sure the bed base in the shop is similar to the one you have at home, because fixed slats or a hard surface change how a mattress feels.

CHOICE also says some mattress-in-a-box models offer adjustable firmness that you can configure at home.

Before you buy

Read a brand's firmness label as that brand's own claim.
Try the mattress on a base like your own, as CHOICE suggests.

The bed.chat checklist covers firmness with the other checks before you pay. For a personal answer, Bed Fit, the chooser on the bed.chat home page, asks nine quick questions and tells you the mattress type, firmness range and size for your country.