How Thick Should a Mattress Be?
The ideal mattress thickness in the UK is usually between 20cm and 30cm for most adults. This range balances comfort, support and compatibility with standard bed frames, though the right depth depends on your body weight, sleeping position, frame type and whether you need extra height for ease of getting in and out of bed.
What Does Mattress Thickness Mean?
Mattress thickness, also called depth, is the measurement from the base to the top surface in centimetres. UK standard sizes such as a double 135x190cm (4ft6) or king 150x200cm (5ft) are width and length; thickness is separate. Depths below 15cm are generally suited to children or occasional use, while those above 30cm are premium models that may require deeper bed frames.
Recommended Mattress Depths by Sleeper Type
Side sleepers often benefit from 23-28cm depths that allow shoulder and hip sink for pressure relief. Back and stomach sleepers usually need 20-25cm for firmer support to keep the spine aligned. Heavier adults (over 95kg) should consider thicker mattresses of at least 25cm to prevent bottoming out. Lighter sleepers under 60kg can use 18-23cm without issue.
Use this decision rule: add your body weight in kg to your age in years; if the total exceeds 150, choose at least 25cm depth. Check the specific product page for exact mattress depth before ordering.
Checklist for Choosing Thickness
- Measure the internal height of your bed frame from the slat or base surface to the top rail.
- Add at least 5cm clearance so the mattress sits proud of the frame for easy sheet tucking.
- Ensure the top-bunk guard rail on any bunk bed will rise at least 16cm above the mattress surface to meet BS EN 747; use the maximum mattress depth the bed maker states.
- Factor in any mattress topper you plan to add (typically 5cm).
- Confirm the assembled bed height feels right for your mobility; taller mattresses make getting up easier.
Mattress Thickness and Bed Frame Compatibility
Most wooden and metal bed frames in the UK are designed for mattresses between 20cm and 25cm. A mattress that is too thick can make the bed feel unstable or prevent proper sheet fitting. Conversely, a mattress under 15cm on a high-sided frame can leave you feeling low. For storage beds or divans, deeper mattresses reduce the usable storage volume underneath.
When buying a new frame, match it to your chosen mattress depth. Wooden beds often suit classic sprung models, while metal frames work well with most types. Leather beds may need extra depth to maintain proportions.
Thickness for Children’s and Toddler Mattresses
Cot mattresses are commonly 60x120cm and around 10-15cm thick to fit standard cots safely. Cot bed and toddler beds (70x140cm) usually take 12-18cm depths. For bunk beds, never exceed the manufacturer’s stated maximum mattress depth so the guard rail remains at least 16cm above the mattress; top bunks are not recommended for children under 6. All UK mattresses must meet BS 7177 fire safety rules.
Look for specialist children’s options such as the Jay-Be® Toddler Anti-Allergy Micro e-Pocket™ Mattress for smaller frames where thin, supportive depth is essential.
Types of Mattress and How Thickness Affects Performance
Memory foam mattresses (often 20-25cm) contour closely but can feel warmer; thicker versions add plushness. Hybrid and pocket sprung models in the 25-30cm range combine support layers with comfort. Thinner foam-free sprung mattresses (around 18-22cm) offer cooler sleep and are easier to rotate.
For memory foam, consider the memory foam mattress range. Hybrid buyers may prefer Jay-Be® Benchmark S5 Hybrid e-Sprung™ Eco-Friendly Mattress for balanced depth and support. Those wanting firmer feel without excessive thickness can choose the Apollo Hera Ortho Comfort Mattress.
Practical Tips for Measuring and Testing
Measure your current mattress depth with a tape from floor to top when on the bed base. Lie on the mattress in your usual position for at least 15 minutes in store if possible. Check that your shoulders and hips sink appropriately without the base being felt. Remember UK upholstered mattresses must comply with 1988 fire safety regulations.
If your frame has high sides, add a 5-7cm topper only after confirming total depth will not exceed frame limits. For adjustable beds, thinner mattresses (under 20cm) usually flex better.
| Sleeper Profile | Recommended Thickness | Typical Use |
|---|---|---|
| Child / Toddler | 10-18cm | Cot, cot bed, bunk (check BS EN 747 rail height) |
| Light adult side sleeper | 20-25cm | Standard single 90x190cm or small double 120x190cm |
| Average adult back sleeper | 23-28cm | Double 135x190cm or king 150x200cm |
| Heavier adult | 25-30cm+ | King or super king 180x200cm with sturdy frame |
Always verify exact mattress depth on the individual product page as specifications vary. If you need extra height, pair a standard depth mattress with a deeper divan or storage bed from the range.
Shop the full mattress collection or narrow by size with single mattresses. For wooden frames that suit most depths see wooden beds.
Our picks for this guide
- Jay-Be® Benchmark S5 Hybrid e-Sprung™ Eco-Friendly Mattress – Offers a balanced hybrid depth that suits most UK bed frames while delivering strong support for average weight adults.
- Apollo Hera Ortho Comfort Mattress – Provides firm orthopaedic support at a practical thickness ideal for back sleepers and those needing spinal alignment on standard frames.
- Jay-Be® Toddler Anti-Allergy Micro e-Pocket™ Mattress – Slim profile designed specifically for toddler and cot beds, meeting safety rail requirements while remaining supportive.
- Jay-Be® Benchmark S3 Memory Eco-Friendly Mattress – Memory foam construction at a comfortable depth that contours well for side sleepers without excessive height.
Frequently asked questions
Is a thicker mattress always better?
No. While thicker mattresses (25-30cm) often provide more comfort layers, they are not automatically superior. A 20cm well-constructed hybrid can outperform a 30cm poorly made one. Choose based on support needs, frame compatibility and sleeping position rather than maximum depth. Check the exact product specifications.
Can I use a thick mattress on a divan bed?
Yes, provided the total height suits your room and mobility. Most divans accept 20-28cm mattresses. Deeper mattresses reduce the visible divan height and may limit storage drawer access on storage beds. Measure the divan platform and add the mattress depth to check the final bed height.
What thickness is best for a folding guest bed?
Folding beds usually perform best with 10-15cm mattresses to allow easy folding and storage. The Jay-Be® range offers compact models with suitable thin eco-friendly mattresses that still provide decent comfort for occasional adult guests. Thicker options may not fold correctly.
Does mattress thickness affect temperature?
Yes. Thicker memory foam layers (over 25cm) can retain more heat. Thinner foam-free or hybrid mattresses around 20cm often sleep cooler because air circulates better through springs. Consider your preferred sleep temperature when choosing depth and materials.
How does EU mattress size differ from UK?
EU single is typically 90x200cm compared with UK single 90x190cm; EU double is 140x200cm versus UK double 135x190cm. Depths are similar but always confirm exact measurements. UK beds rarely fit EU sizes without gap or overhang, so match both length and width.