To choose a mattress, start with how you sleep and your body, then work through type, firmness, size, base, trial and price. A mattress should keep your spine aligned when you sleep, which can depend on your body type and sleeping position, CHOICE says. Comfort is subjective, but understanding firmness and mattress types helps narrow the choice when you test in store, CHOICE's buying guide notes.
1. Begin with how you sleep and your body
Your usual sleep position points to a starting level of support. 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, CHOICE reports. For side or mixed sleepers, the practical check is whether the mattress holds your body without a gap at the waist.
A mattress does not have to be firm to be beneficial, as long as it supports your body, Which? found in its tests. Judge by how your shoulders, hips and back feel held, not by the firmness word on the tag.
2. Any pain: general guidance only
If pain keeps you up or lasts, see a doctor or physiotherapist; bed.chat does not diagnose or treat pain, as its about page states. A mattress is a support and comfort choice, not a medical device. When pain is ongoing, get professional advice before you shop.
3. Heat and a partner
Sharing a bed adds motion. A mattress that jiggles when your partner turns can disturb sleep, so Which? measures stability to see if you feel that movement. Its testing also shows memory foam mattresses absorb impact well, making them particularly suitable for light sleepers who share with a fidget, Which? reports.
The heat side is not covered by a published test in this guide. Bed Fit on the home page asks whether you sleep hot so you can note it, but no tester here makes a cooling claim.
4. Type of mattress
Foam or spring? CHOICE's tests found no evidence that foam or spring mattresses suit particular sleeping positions, and neither type is objectively better. Its foam vs spring explainer says the claims about position-fitting are not backed up. Pick the type you find comfortable, not the one a label says matches your posture.
Consumer Reports staff buy every mattress they test from retail stores to keep objectivity, the US group says.
5. Firmness range
Which? warns that many brands define firmness and softness however they want, outside the official standard, so you cannot rely on those claims to compare brands. Use the store test and your own back sense, and treat any number scale as the brand's own language.
6. Size in your country
Buy the largest bed your room can fit, and make sure the mattress is at least 10–15 cm longer than the tallest person sleeping on it, CHOICE reports from retailers and manufacturers. Length matters more than the marketing name.
Sizes differ by country. The bed.chat checklist notes a UK King (150 × 200 cm) is about the size of a US Queen (60 × 80 in, about 152 × 203 cm). Always measure the frame you have.
| Label | Size given |
|---|---|
| UK King | 150 × 200 cm |
| US Queen | 60 × 80 in (about 152 × 203 cm) |
The bed.chat size tool lists mattress sizes for the US, UK, Canada, Australia, New Zealand and Ireland in centimetres and inches.
7. The frame you will put it on
Match the bed base in the store to the one at home. Fixed slats or a hard surface change how a mattress feels, so a soft mattress on a hard base feels different from the ensemble base in the shop, CHOICE advises.
When trying a bed, lie down the same way you would at home. Which? says the mattress should mould to your body while supporting it.
Many manufacturers stipulate a minimum distance between bed slats and the mattress, and some require photo evidence of this for returns, Which? says. Check your frame's slat gap before you buy.
8. Trial, returns and warranty
Most online-only mattresses come with a sleep trial; some start at 40 nights and others last up to a year, Which? says. A trial lets you test at home, but read the return condition, including any slat-distance photo rule above.
The bed.chat checklist lists ten before-you-buy checks including trial and returns, warranty sag depth, and frame and warranty terms. Use it before you pay.
9. The real price
A high price tag is not a comfort guarantee. CHOICE testers regularly find more affordable mattresses that score as well as or better for comfort than ones costing thousands of dollars, CHOICE reports. There is no correlation between a mattress's spring count and its comfort, the same source adds. Pay for support and size that fit you, not for spring numbers or a prestige name.
Before you pay
The bed.chat checklist gives ten things to check for any mattress: firmness, certifications, foam density, size, frame and warranty, bed height for an older sleeper, trial and returns, UK online cancellation, warranty sag depth, and the "was" price. For a personal answer, Bed Fit on the bed.chat home page asks nine quick questions and tells you the mattress type, firmness range and size for your country, plus what to check before you pay.
Sources
- CHOICE: How to choose the right mattress
- CHOICE: How we test mattresses
- CHOICE: Foam vs spring mattresses
- CHOICE: Buying a new bed? We debunk 5 mattress myths
- Which?: Best mattresses 2026 (how to buy the best mattress)
- Which?: Best mattresses for side sleepers
- Which?: How to buy the best bed frame
- Which?: How we test mattresses
- Which?: Best memory foam mattresses
- Which?: How to return a mattress
- Consumer Reports: Mattress buying guide
- Consumer Reports: How We Test Mattresses