1. Buying too firm "for your back"#

The biggest myth in mattress buying. The evidence favours medium-firm, not firm, for comfort, sleep quality and spinal alignment in most people,1 and a very firm mattress can actually worsen back pain. Start at medium-firm and adjust for your body.

2. Ignoring your sleeping position#

Your position is the single biggest clue to the feel you need, softer for side sleepers, firmer for front sleepers. Buying without considering it is how people end up with sore shoulders or aching backs. See our sleeping position guide.

3. Judging a mattress in a showroom#

Five minutes lying down tells you almost nothing. Comfort depends on the interaction between sleeper and surface over a full night, and it takes weeks to adapt.2 Always buy with a proper home trial.

4. Skipping the trial period or returns terms#

A long trial is your safety net. Check how long it is, whether it's genuinely free, and whether made-to-order items are excluded before you buy.

5. Falling for the RRP discount#

Many brands list a high reference price and "discount" heavily from it. Judge value on the price you actually pay on the day, not the headline saving.

6. Forgetting about temperature#

If you sleep hot, a dense all-foam mattress can make it worse. Favour breathable hybrids, latex or cooling covers, see our cooling guide.

7. Overlooking durability#

Cheap, low-density foam softens fast, while quality foams and springs hold their feel for years.3 A slightly higher upfront price often costs less per year of good sleep.

8. Buying the wrong size#

Couples in particular underestimate how much space they need. Sizing up usually improves sleep more than almost any other upgrade, see our UK sizes guide.

9. Neglecting the base and the pillow#

A great mattress on a sagging base, or paired with the wrong pillow, won't deliver. Both affect support and alignment, see our pillow guide.

10. Keeping an old mattress too long#

Support and hygiene both degrade over years of use. If you wake stiff, or your mattress is sagging or past its warranty, it's time, see our when to replace guide.

Ready to choose well? Browse the full range or take our quiz for a personalised match.

References#

  1. 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
  2. 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
  3. 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