Firm Mattresses Compared & Scored (2026)

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If you're heavier or sleep on your front, a firm mattress is more likely to keep your hips level with your shoulders, though your comfort also depends on how deeply you settle into the top layer. For a bad back, choosing harder deserves more caution.

Read "firm" within the maker's own range: Bed Advice UK says there's no industry-wide standard for comparing firmness between makers. Another maker's medium-firm could feel similar. Firm is still sold as the grown-up choice.

Firm suits greater body weight and front sleeping

More body weight presses further into the same comfort layer, so a mattress that feels medium under a lighter body can feel soft under you if you're heavier, which explains Bed Advice UK's advice to choose firmer tension as weight increases. Compare cushioning depth alongside tension when choosing a mattress for a heavier body.

Face down, you'll arch your lower back if your pelvis drops below your ribs on a soft surface. Look for enough resistance beneath your hips when comparing mattresses for front sleeping, while keeping a comfortable top layer.

Back pain and side sleeping need a different starting point

Before choosing firm for back pain, start a step softer: Caggiari and colleagues' review of 39 articles identifies medium-firm as the best-supported starting point for non-specific low back pain. A hard bed isn't necessarily needed for a bad back, as Bed Advice UK also advises.

On your side, your shoulder needs room to sink into the top layer, so avoid a firm surface with too little cushioning to accommodate it. Orthopaedic is a maker's word for firmer, not a regulated medical category.

Allow at least 10 minutes lying in your normal sleeping position to judge the feel. See a GP if your back pain hasn't improved after a few weeks of treating it at home, as the NHS advises.