How Deep Should a Mattress Be? UK Depth Guide
Mattress depth in the UK typically ranges from 15cm to 30cm for most adult beds, with 20-25cm offering a balance of comfort, support and compatibility with standard bed frames. Shallower mattresses suit platform beds or bunk beds while deeper ones provide extra cushioning but may need taller sides or divan bases.
What is Mattress Depth?
Mattress depth, also called thickness, is the vertical measurement from the base to the sleeping surface. UK regulations require all mattresses to meet BS 7177 fire safety standards regardless of depth. Depth affects how the mattress feels, how well it fits your bed frame and whether you need a mattress protector or topper.
Small single (75x190cm), single (90x190cm), small double (120x190cm), double (135x190cm), king (150x200cm) and super king (180x200cm) sizes are all available in varying depths. EU sizes differ slightly, for example an EU double is 140x200cm, so always confirm exact measurements before buying.
Standard Mattress Depths in the UK
Most UK mattresses fall into three categories:
- Shallow: 15-20cm – ideal for bunk beds, folding beds, children's beds and low platform frames.
- Medium: 20-25cm – the most common depth for everyday use with wooden bed frames or metal bed frames.
- Deep: 25-30cm+ – provides luxury cushioning and works best with divan bases or storage beds that have higher sides.
Top bunks must follow BS EN 747 with guard rails rising at least 16cm above the mattress surface. Always use the maximum mattress depth stated by the bed maker for safety; top bunks are not recommended for children under 6.
How Depth Affects Comfort and Support
Deeper mattresses often incorporate more layers of foam or pocket springs, allowing better pressure relief at the shoulders and hips. A 15cm foam mattress may feel firmer than a 25cm hybrid because it has less material to compress. However, excessive depth without proper support can cause sinking.
Memory foam mattresses in particular benefit from 22cm or more to allow the foam to contour without bottoming out. Hybrid designs with pocket springs plus foam layers usually perform well from 20cm upwards. Check the product page for exact specs as only the name is used here.
Checklist for Choosing Depth by Sleeping Position
- Side sleepers: choose at least 22cm depth for shoulder and hip cushioning.
- Back or stomach sleepers: 18-23cm usually provides sufficient lumbar support.
- Combination sleepers: 20-27cm hybrids give versatility.
- Heavier adults: deeper mattresses (24cm+) resist compression better.
Bed Frame Compatibility and Depth
Your bed frame determines suitable mattress depth. Wooden bed frames and metal bed frames often have slats or a platform that can accommodate 20-25cm mattresses without the mattress sitting too high. Check the frame's side rail height; the mattress should not rise more than 5-8cm above the rails for safety and appearance.
Storage beds and fabric beds may need shallower mattresses (under 20cm) so drawers or lift-up mechanisms close properly. Leather beds and divans usually accept deeper models. Always measure your frame's internal depth and add the mattress depth to ensure the total height works with bedside tables.
See our range of Wooden Beds and Metal Bed Frames to match with the right depth mattress.
Mattress Depth for Children's and Specialty Beds
Cot mattresses are commonly 60x120cm and around 10-15cm deep to fit safely inside cot sides. Cot bed and toddler bed mattresses measure 70x140cm and are typically 10-12cm. For bunk beds and children's beds, stay at or below the manufacturer's maximum depth to keep guard rails effective.
Our Kids' Beds collection includes options designed for specific mattress depths. Folding and guest beds often use 15cm mattresses for easy storage.
Practical Decision Rules and Checklist
Use this checklist before purchase:
- Measure your bed frame's side height and internal base-to-rail distance.
- Decide on base type: platform, sprung slats or divan.
- Match depth to your weight and sleeping position.
- Ensure fire safety labels are present (all UK mattresses meet 1988 regulations).
- Consider adding a mattress protector to maintain hygiene without significantly changing feel.
- Check whether a thin mattress topper could adjust an existing mattress instead of buying deeper.
For memory foam options, explore Memory Foam Mattresses. Many Noomi, Flair, Solace+Co, Maxitex and Recoil models are available in depths that suit standard UK frames.
When to Choose Deeper or Shallower Mattresses
Choose deeper (25cm+) if you want luxury hotel-style cushioning or suffer from pressure points. Shallower (15-20cm) suits minimalist rooms, loft beds, or when replacing an old deep mattress on a low frame. Hybrids often perform best in the 22-27cm range because the spring unit takes up space, leaving room for comfort layers.
Always verify exact depth on the individual product page as specifications vary by model. A deeper mattress on a low frame can make getting in and out of bed harder, especially for older users or those with mobility issues.
| Bed Type | Recommended Depth | Reason |
|---|---|---|
| Standard wooden or metal frame | 20-25cm | Good balance of support and aesthetics |
| Bunk or children's bed | 15-18cm | Maintains guard rail height per BS EN 747 |
| Storage or ottoman bed | 18-22cm | Allows mechanism clearance |
| Divan base | 22-30cm | Matches traditional taller look |
Our full Mattresses range includes models across these depths. For quick options see Free Next Day Delivery Beds.
Our picks for this guide
- Jay-Be® Benchmark S3 Memory Eco-Friendly Mattress – This memory foam mattress sits in the popular 20-25cm depth range, offering good pressure relief while fitting most standard wooden and metal UK bed frames.
- Jay-Be® Benchmark S5 Hybrid e-Sprung™ Eco-Friendly Mattress – A hybrid design typically around 22-27cm that balances support and comfort, making it suitable for a wide range of bed frames including storage beds.
- Jay-Be® Toddler Anti-Allergy Micro e-Pocket™ Mattress – Shallow depth designed specifically for toddler beds and cots, keeping safety rails effective while meeting UK fire regulations.
- Jay-Be® Hybrid 2000 e-Pocket™ Truecore® Eco-Friendly Mattress – Deeper hybrid construction provides extra cushioning layers, ideal for king and super king frames where additional comfort is desired.
Frequently asked questions
Does a deeper mattress last longer?
Not necessarily. Durability depends more on materials and construction than depth alone. A well-made 20cm hybrid can outlast a poorly constructed 28cm mattress. Check the product page for details on springs, foam density and cover quality.
Can I use a deep mattress on a divan base?
Yes. Divans are designed for deeper mattresses, typically 22-30cm. The combination gives a traditional high bed look. Measure total height to ensure it works with your bedroom furniture and is easy to get in and out of.
What depth mattress is best for a folding bed?
Most folding beds work best with 15cm mattresses to allow compact folding and storage. Shallower depths also reduce weight.
Should I buy a mattress topper instead of a deeper mattress?
A topper can add 5-8cm of cushioning to an existing mattress. It is a cheaper way to adjust firmness or comfort without replacing the whole bed. However, it will not improve core support the way a properly constructed deeper mattress can.
Is there a maximum mattress depth for UK bunk beds?
Yes. The top bunk guard rail must rise at least 16cm above the mattress. Use only the maximum depth the bed manufacturer states. All UK bunk beds must comply with BS EN 747.