Two numbers decide which mattress a child's bed needs: the size and the depth. The size has to match the bed exactly, and on a bunk bed, high sleeper or mid sleeper the depth is a safety figure, not a comfort preference. Most raised beds take a mattress no deeper than 15 or 16cm, and a trundle needs one of around 10cm.
This guide covers every UK kids' mattress size, the right depth for each type of bed, how many mattresses you'll need, and how to choose and look after one.
On this page
UK kids' mattress sizes
| Size | Dimensions | In feet |
|---|---|---|
| Cot bed | 70 x 140cm | 2ft 3in x 4ft 7in |
| Shorty | 75 x 175cm | 2ft 6in x 5ft 9in |
| Small single | 75 x 190cm | 2ft 6in x 6ft 3in |
| Single | 90 x 190cm | 3ft x 6ft 3in |
| Continental single | 90 x 200cm | 3ft x 6ft 6in |
| Small double | 120 x 190cm | 4ft x 6ft 3in |
| Continental small double | 120 x 200cm | 4ft x 6ft 6in |
| Double | 135 x 190cm | 4ft 6in x 6ft 3in |
| Continental double | 140 x 200cm | 4ft 6in x 6ft 6in |
Two sizes people miss. A shorty is 175cm long, 15cm shorter than a single, so a shorty bed needs a shorty mattress. Continental sizes are 200cm long rather than 190cm, and they need a continental mattress. Both are easy mistakes, and expensive ones.
For bed frame sizes, see our kids' bed size guide.
Depth: the safety number
| Bed type | Maximum depth | Why |
|---|---|---|
| Bunk bed, top bunk | Usually 15 to 16cm | So the guard rail stays high enough |
| High sleeper | Usually 15 to 16cm | So the guard rail stays high enough |
| Mid sleeper | Usually 15 to 16cm | So the guard rail stays high enough |
| Trundle bed | Around 10cm | It has to slide under the bed above |
| Bottom bunk | More flexible, but check | Head clearance to the bunk above |
| Standard bed frame | Check the product page | Mostly a matter of comfort |
Guard rails are designed to sit a set height above the mattress. Most high-street single mattresses are 20cm or deeper, which takes 5cm or more off that height and stops the rail doing its job properly. The exact limit varies between beds and is set by the manufacturer, so always check it on your bed's product page.
How many will you need?
- Single bed: one.
- Bunk bed: two.
- Bunk bed with a trundle: three, and the trundle one is slimmer.
- Guest bed with a trundle: two, one of them slim.
- Family or double bunk: a double or small double for the bottom, depending on the bed, and a single for the top, plus a trundle mattress if fitted. See our double bunk bed guide.
It sounds obvious, but it's the thing most often forgotten at checkout.
Our kids' mattresses
Our own range is made in the UK and arrives vacuum packed and rolled, so it goes up the stairs easily.
15cm, for raised beds
MemoryDream 15
Memory foam over a reflex layer: contouring, quiet and medium-firm. The one most parents choose.
Sizes and details
15cm, for raised beds
PocketRest 15
Pocket springs under memory foam. More airflow, so it sleeps cooler, with a little bounce.
Sizes and details
15cm, for raised beds
ComfortSleep 15
Reflex foam with a medium feel. Our best-value option, and good for guest and occasional beds.
Sizes and details
15cm, fully waterproof
DryComfort 15
Waterproof all the way through for bedwetting and accidents, with a removable cover.
Sizes and details
10cm, for trundles
TrundleEase 10
Slim enough to slide under the main bed. A standard mattress won't fit a trundle.
Sizes and details
18cm, for normal beds only
MemoryTeen 18
Deeper memory foam for taller, heavier teenagers. Too deep for a bunk bed or high sleeper.
Sizes and detailsAlso in the range: the British Made High-Density Shorty Mattress for shorty beds, and the Pippa Pocket Sprung, Florence Memory Sprung and Guardian Orthopaedic sprung mattresses. Check the stated depth of each against your bed's maximum before using one on a raised bed. For teenagers and adults on standard frames, see our full depth mattresses. Our guide to the best single mattress for kids compares our picks in more detail.
Which type, and how firm?
| Type | Feel | Best for |
|---|---|---|
| Reflex foam | Supportive, medium | Younger children, guest beds, a tighter budget |
| Memory foam | Contouring and quiet | Most children, restless sleepers |
| Pocket sprung | Traditional, with some bounce | Children who sleep hot, as springs let more air through |
For most children, medium to medium-firm is right: supportive enough for a growing spine, with enough give to be comfortable. Babies and toddlers need a firm, flat mattress, in line with safer sleep guidance.
Particular situations
- A child who sleeps hot. Pocket springs let more air through than foam. A top bunk is usually a degree or two warmer than the bottom, so a lighter duvet can be the cheaper fix. See our guide to room temperature and sleep.
- Bedwetting or frequent accidents. A waterproof protector is the first line of defence, and it costs a fraction of a new mattress. For a longer phase, the fully waterproof DryComfort 15 is the better answer.
- Allergies. A removable, washable cover and a protector keep dust mites down. Wash bedding hot and vacuum the mattress monthly.
- A tall teenager. A continental size 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. It's the biggest single factor in how long a child's mattress lasts.
- Rotate it head to foot every three months. Most children's mattresses are one-sided, so rotate rather than flip unless the label says otherwise.
- Vacuum it monthly with the upholstery attachment, and air it by pulling the bedding back for an hour before making the bed.
- Give a rolled mattress time to expand, usually 24 to 48 hours after unwrapping.
A children's mattress usually lasts five to seven years, and many are replaced sooner because the child has outgrown the size. Replace one sooner if it sags, is damaged, or keeps smelling after cleaning. See our guides to how often to change a mattress and cleaning 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 a 200cm length. The mattress should fit snugly, with no big gaps at the sides or ends.
What depth mattress for a bunk bed?
Usually 15 or 16cm at most on the top bunk. Check the figure on your bed's product page, as it varies by model.
Can I use a normal mattress on a trundle bed?
No. A trundle needs a slim mattress, around 10cm, so it slides under the bed above. The TrundleEase 10 is made for this.
Is memory foam safe for children?
Yes, on a bed that suits their age. Memory foam holds a little more heat than springs, so a pocket sprung mattress may suit a child who sleeps hot.
Firm or soft for a child?
Supportive rather than soft. Medium to medium-firm suits most children, and babies and toddlers need a firm, flat mattress.
What's the difference between a shorty and a small single?
Length. A shorty is 175cm long and a 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, with the trundle one slimmer.
How long does a children's mattress last?
Five to seven years, though most are replaced because the child has outgrown the size rather than because the mattress has worn out.
Find the right size and depth
UK-made kids' mattresses in every size, including 15cm for bunk beds and high sleepers.
Shop kids' mattressesBuying for a raised bed? See our bunk bed mattresses and the bunk bed mattress guide.