What Firmness Level Mattress Do I Need? UK Guide
The firmness level you need in a mattress depends mainly on your body weight, sleeping position and personal comfort preference. Most people in the UK find medium or medium-firm mattresses suit them best, but heavier sleepers often need firmer support while lighter sleepers and side sleepers may prefer softer options that cushion pressure points.
How Mattress Firmness Affects Comfort and Support
Firmness describes how much a mattress resists sinking under your body. A soft mattress allows deeper sinkage for pressure relief. Medium offers balanced support and cushioning. Firm provides strong resistance, keeping the spine aligned for those who need it. UK standard mattress sizes range from small single 75x190cm (2ft6) to super king 180x200cm (6ft); choose firmness independently of size but ensure the base matches exactly.
Check the product page for exact specifications on each mattress. Trade-off: softer mattresses can feel too sinky for stomach sleepers, while firm ones may feel hard on shoulders for side sleepers.
Firmness Recommendations by Sleeping Position
Back sleepers usually need medium to firm support to maintain natural spinal alignment. Side sleepers benefit from softer or medium options that allow the shoulder and hip to sink slightly. Stomach sleepers require firmer mattresses to prevent the hips from dipping and straining the lower back.
- Side sleeping: aim for soft to medium to cushion pressure points at shoulders and hips.
- Back sleeping: medium to firm for even weight distribution.
- Stomach sleeping: firm or ultra-firm to keep hips from sinking.
A practical checklist: lie in your usual position for at least 15 minutes in store if possible. Measure the gap under your lower back with your hand; it should be minimal on the right firmness.
Combination Sleepers
If you change position often, choose medium or medium firm mattresses as they adapt better than extremes. Hybrid and pocket sprung constructions help here.
Firmness Guidance by Body Weight
Body weight is one of the strongest predictors of suitable firmness. Lighter people (under 60kg) often need softer mattresses because they do not compress firmer ones enough. Average weight (60-90kg) usually suits medium. Heavier sleepers (over 90kg) require firm support to stop excessive sinkage and maintain spinal alignment.
Decision rule: add 1 firmness point for every 15kg above 80kg. Subtract 1 point for every 15kg below 60kg. Always test if possible. For children, firmer surfaces are generally safer; see our range of kids mattresses.
Popular Mattress Types and Their Firmness Profiles
Memory foam tends to feel softer and more contouring. Pocket sprung offers responsive support that can be tuned from medium to firm. Hybrids combine both. Latex provides a firmer, more responsive feel with good bounce. Open coil is often firmer and better value but less isolating.
Check each product page for exact construction details. UK law requires all mattresses to meet BS 7177 fire safety. For eco-conscious buyers, natural fillings often come in medium to firm profiles.
If you like memory foam, browse our memory foam mattresses. Those wanting strong support should look at firm mattresses.
Practical Checklist Before You Buy
- Record your weight and primary sleeping position.
- Decide your preferred sink level: do you like to feel hugged or supported on top?
- Measure your current mattress depth and compare with new options (use maximum allowed by any bed frame).
- Consider a partner: you may need a firmer side or split firmness if weights differ by more than 30kg.
- Check for edge support if you sit on the bed often.
- Visit the Birstall showroom to test similar firmness levels side by side.
One useful comparison table of general firmness suitability:
| Body Weight | Side Sleeper | Back Sleeper | Stomach Sleeper |
|---|---|---|---|
| Under 60kg | Soft | Medium | Medium-Firm |
| 60-90kg | Medium | Medium-Firm | Firm |
| Over 90kg | Medium-Firm | Firm | Ultra Firm |
Recommended Products for Different Firmness Needs
Many buyers start with versatile medium-firm options. For firmer support, consider the Maxitex Foamapaedic Firm Foam Mattress. The SOLACE+CO Plant Based Eco Memory Foam Mattress offers a balanced medium feel with pressure relief ideal for side sleepers who want some sink. If you prefer a responsive hybrid, the Jay-Be® Firm Hybrid 2000 e-Pocket™ Truecore® Eco-Friendly Mattress gives excellent spinal support without feeling board-like. For those wanting maximum firmness, the Komfi Vitality Ultra Firm Foam Mattress provides the solid platform that very heavy sleepers or stomach sleepers often require.
Explore the full selection in our mattresses category or narrow by size such as king size mattresses.
Our picks for this guide
- Maxitex Foamapaedic Firm Foam Mattress – Delivers the strong resistance needed by heavier back and stomach sleepers.
- SOLACE+CO Plant Based Eco Memory Foam Mattress – Provides balanced medium contouring ideal for average-weight side sleepers.
- Jay-Be® Firm Hybrid 2000 e-Pocket™ Truecore® Eco-Friendly Mattress – Offers responsive firm support suitable for combination sleepers and those over 80kg.
- Komfi Vitality Ultra Firm Foam Mattress – Gives maximum firmness for very heavy sleepers or strict stomach sleepers.
Frequently asked questions
Can I change mattress firmness after purchase?
Most retailers do not allow returns solely for firmness preference once the mattress has been slept on, due to hygiene rules. Test thoroughly in store or use any available showroom display models. Measure your current comfort gap with your hand flat under the lower back to judge before buying.
Is a firm mattress always better for bad backs?
Not necessarily. While firm support helps heavier people and stomach sleepers maintain alignment, side sleepers with back pain often need medium mattresses that cushion the shoulder and hip. The right firmness keeps the spine neutral; too firm can create pressure points. Check product pages for exact support layers.
What firmness is best for children and teenagers?
Most UK experts recommend medium to firm mattresses for children to support growing spines. Top bunks must use the maximum mattress depth stated by the maker and comply with BS EN 747 (guard rail at least 16cm above mattress). Avoid very soft options for under-6s. See kids pocket sprung and memory foam ranges.
Do memory foam mattresses run firmer or softer than pocket sprung?
Memory foam usually feels softer and more hugging because it contours slowly. Pocket sprung can be engineered from soft to firm depending on coil count and padding. Hybrids combine the two. Always read the exact description on the product page and test if possible.
How does room temperature affect perceived firmness?
Cooler rooms can make memory foam feel firmer because the foam stiffens. Warmer conditions make it softer. Pocket sprung and latex are less affected. If your bedroom is cold, you may need to choose one firmness level softer than usual to compensate.
Related guides
- Latex Mattress Firmness Guide: Choosing the Right Level
- Pocket Sprung Mattress Firmness Levels Explained
- Mattress Tog Rating Explained – Which Tog Do You Need?
- How to Stop a Mattress from Sagging – Construction and Firmness Tips
- Do You Need to Turn a Pocket Sprung Mattress?
- Do You Need to Turn a Hybrid Mattress?