Two numbers decide this: the size, and the depth.
Size is obvious. Depth is the one that catches people out, because on a bunk bed or high sleeper it's a safety figure, not a comfort preference.
UK mattress sizes
| Size | Dimensions | Also called |
|---|---|---|
| Cot bed | 70 x 140cm | 2ft3 x 4ft7 |
| Shorty | 75 x 175cm | 2ft6 x 5ft9 |
| Small single | 75 x 190cm | 2ft6 x 6ft3 |
| Single | 90 x 190cm | 3ft x 6ft3 |
| Continental single | 90 x 200cm | 3ft x 6ft6, European single |
| Small double | 120 x 190cm | 4ft x 6ft3 |
| Continental small double | 120 x 200cm | 4ft x 6ft6 |
| Double | 135 x 190cm | 4ft6 x 6ft3 |
| Continental double | 140 x 200cm | 4ft6 x 6ft6 |
Two sizes people miss. Shorty at 175cm is 15cm shorter than a standard single, and a shorty bed needs a shorty mattress. Continental sizes are 200cm rather than 190cm, and they need a continental mattress. Both are easy mistakes and expensive ones.
Depth: the safety number
| Bed type | Maximum depth | Why |
|---|---|---|
| Bunk bed, top bunk | 15–16cm | Guard rail clearance |
| High sleeper | 15–16cm | Guard rail clearance |
| Mid sleeper | 15–16cm | Guard rail clearance |
| Trundle bed | Around 10cm | Must clear the frame above when it slides away |
| Bottom bunk | Usually no limit | No rail above it |
| Standard bed frame | No limit | Choose on comfort |
Guard rails are designed to sit a set height above the mattress surface. Most high-street single mattresses are 20cm or deeper, which removes 5cm of that clearance and stops the rail doing its job.
Check the specific figure on your bed's product page. It varies between models, and the bed manufacturer sets it.
How many will you need?
- Single bed: one
- Bunk bed: two
- Bunk with a trundle: three, and the trundle one is shallower
- Guest bed with a trundle: two
- Family bunk: a small double and a single, plus a trundle mattress if fitted
Sounds obvious, and it's the single most common thing forgotten at checkout.
Our range
All made in the UK, all vacuum packed and rolled so they come upstairs easily.
For bunk beds, high sleepers and mid sleepers — 15cm
ComfortSleep 15, from £160
Reflex foam. Firm, supportive, and the most affordable of the three. Good for younger children, lighter body weights, and beds that won't get nightly use.
Shorty, small single, single, continental single, small double, continental small double, double, continental double.
MemoryDream 15, from £220
Memory foam over a reflex base. Contours to the body, quiet, and the one most parents choose. Slightly warmer than sprung.
Same eight sizes.
PocketRest 15, from £230
Pocket springs. More airflow so it sleeps cooler, with a traditional feel and a bit of bounce. The choice for a child who runs hot.
Single, continental single, small double, double.
For trundles and pull-out beds — 10cm
TrundleEase 10, from £130
Built at 10cm so it clears the frame above when the trundle slides back. A standard mattress won't fit.
Shorty, small single, single, continental single, small double, continental small double, double, continental double.
For teenagers on a normal bed frame — 18cm
MemoryTeen 18, from £260
Deeper memory foam, built for a heavier, taller body. Not suitable for a bunk or high sleeper, since it exceeds the guard rail clearance. It's one of the genuine advantages of choosing a floor-level bed for a teenager.
Single, small double, double, king.
Also in the range
- Guardian Orthopaedic Sprung Mattress — firmer sprung support
- Pippa Pocket Sprung Mattress
- Florence Memory Sprung Mattress
- British Made High-Density Shorty Mattress — 75 x 175cm
Check the stated depth on each of these before using them on a raised bed.
For teenagers and adults on standard frames where depth isn't restricted, see our full depth mattress range.
Which type?
| Type | Feel | Best for |
|---|---|---|
| Reflex foam | Firm, supportive | Younger children, guest beds, budget |
| Memory foam | Contouring, quiet | Restless sleepers, most children |
| Pocket sprung | Traditional, some bounce | Children who sleep hot |
For a child, firmer is generally better than softer. A mattress that's too soft doesn't support a spine that's still developing.
Particular situations
A child who sleeps hot. Pocket sprung allows more airflow than foam. Bear in mind a top bunk runs two to three degrees warmer than the bottom, because heat rises, so a lower tog duvet often solves it more cheaply than a different mattress.
Bedwetting or frequent accidents. A waterproof mattress protector is the first line, and it costs a fraction of replacing a mattress. For a child in a longer phase, a fully waterproof mattress is the better answer.
Allergies. A washable cover and a protector do more than the mattress material itself. Wash bedding hot and vacuum the mattress monthly.
A tall teenager. Continental at 200cm gives 10cm more length for no extra floor space. Worth doing before they outgrow a 190cm bed rather than after.
Making it last
- Use a protector from day one. The single biggest factor in how long a child's mattress survives.
- Rotate head to toe every three months. Most children's mattresses are single-sided, so rotate rather than flip unless the label says otherwise.
- Vacuum monthly with the upholstery attachment.
- Air it regularly. Pull the bedding back for an hour before making the bed.
- Allow 24 to 48 hours for a rolled mattress to fully expand after unwrapping.
Children's mattresses typically need replacing every five to seven years, or sooner if outgrown or damaged. More detail in our guide to how often to change a mattress.
Common questions
What size mattress does a child's bed need?
Match it exactly to the bed. A standard single is 90 x 190cm, but shorty beds need 75 x 175cm and continental beds need 200cm lengths.
What depth mattress for a bunk bed?
Usually a 15 or 16cm maximum on the top bunk. Check the figure on your bed's product page, since it varies by model.
Can I use a normal mattress on a trundle bed?
No. Trundles need around 10cm so the mattress clears the frame above when it slides away. The TrundleEase 10 is built for this.
Is memory foam safe for children?
Yes, on a bed appropriate for their age. Choose a breathable one, since foam retains more heat than sprung.
Firm or soft for a child?
Firmer. A mattress that's too soft doesn't properly support a growing spine. Medium to medium-firm suits most children.
What's the difference between shorty and small single?
Length. Shorty is 175cm, small single is 190cm. Both are 75cm wide, and they aren't interchangeable.
Do I need two mattresses for a bunk bed?
Yes, and three if it has a trundle. The trundle one is usually shallower.
How long does a children's mattress last?
Five to seven years typically, though most are replaced because the child has outgrown the size rather than because the mattress has worn out.
Browse our kids' mattress range, or the 15cm bunk bed range if you're buying for a raised bed.
