Choosing a mattress without guessing

1. Work out how you sleep

Side sleepers need the shoulder and hip to sink in; back sleepers need the lumbar curve supported; front sleepers need to not sink at the waist. Most people are one of these most of the night, and that is the single biggest factor.

2. Firmness is personal, support is not

Support means the spine stays level. Firmness is how the surface feels getting there. Two people of different weights need different firmnesses to get the same support — which is why a number on a scale tells you less than ten minutes lying down.

3. Decide about heat early

If you sleep hot, this constrains everything else. Solid memory foam will fight you. Springs, latex and open-cell foams will not.

4. Check the base

A new mattress on a sagging base will feel wrong within months, and no warranty covers it. Press the middle of your base: if it flexes, budget for both.