Getting the size wrong is the most expensive mistake in buying a child's bed, because you usually don't find out until it's built. UK kids' beds run from a cot bed at 70 x 140cm up to a European double at 140 x 200cm. For most children, a standard single at 90 x 190cm lasts from about the age of 3 or 4 into the teens, with a shorty at 75 x 175cm as the space-saving alternative for a small room.
This guide covers every size, when to move up, and the mattress and room checks that catch people out.
On this page
UK bed and mattress sizes
| Size | Mattress | Who it suits |
|---|---|---|
| Cot bed or toddler bed | 70 x 140cm | Toddlers, up to about 4 or 5 |
| Shorty | 75 x 175cm | Younger children in smaller rooms, roughly 3 to 8 |
| Small single | 75 x 190cm | Narrow rooms, from about 4 |
| Single | 90 x 190cm | Most children, from about 3 or 4 into the teens |
| European single | 90 x 200cm | Tall children and teenagers |
| Small double | 120 x 190cm | Teenagers, or a bigger bottom bunk |
| European small double | 120 x 200cm | Tall teenagers |
| Double | 135 x 190cm | Teenagers and adults |
| European double | 140 x 200cm | Teenagers and adults |
Need the adult sizes too? Our UK bed sizes guide covers every size from toddler to super king.
Measure the frame, not the mattress. A bed frame is always bigger than its mattress, and much bigger with a ladder, headboard or storage. When you're checking whether a bed fits a room, use the frame's overall dimensions from the product page.
The size most people don't know exists: shorty
A shorty, 75 x 175cm, is 15cm shorter and 15cm narrower than a standard single. That sounds trivial and isn't: in a small box room, it's often the difference between the bed fitting and not. It suits children up to about 8, so it buys several years.
The trade-off is an extra size along the way, so if the room allows, going straight from a cot bed to a standard single saves a purchase. And a shorty bed needs a shorty mattress; a standard single won't fit. We stock shorty mattresses, which many retailers don't. Browse shorty beds, such as the Tarn Shorty House Bed.
European sizes explained
European sizes, sometimes called continental sizes, are 200cm long rather than 190cm. That extra 10cm matters more than it sounds once a child reaches their teens, and they're common on European-made beds. If your child is already tall for their age, it's worth choosing a European size now rather than replacing the bed at fourteen. The Chelsea high sleeper, for example, takes a European single. Browse all our European single beds.
A 200cm bed needs a 200cm mattress. A standard 190cm mattress leaves a 10cm gap at the end, which is uncomfortable, and on a raised bed a gap is an entrapment risk.
When to move up a size
Forget age brackets and use the bed itself.
The 10cm rule. With your child lying flat, measure from the top of their head to the end of the mattress. Once there's less than 10cm, it's time to plan the next bed.
Other signs it's time:
- They sleep diagonally, or with their feet hanging over the end.
- They regularly wake up pressed against the side of the bed.
- They've stopped wanting to be in it, which is often about space rather than the bed itself.
Children grow in bursts rather than steadily, so a bed that fitted at the start of the school year may not by the summer.
Mattress depth: the one that catches people out
Size isn't the only measurement that matters. Bunk beds, high sleepers and mid sleepers have a maximum mattress depth, usually 15 or 16cm, because 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 the rail's height and stops it doing its job. Trundle beds have their own limit, usually around 10cm, so the mattress slides under the bed above.
Our bunk bed mattresses are made at 15cm for this reason. Always check the maximum depth on your bed's product page, and see our kids' mattress size guide for more.
Matching size to room
Small rooms
A shorty or small single frees up real floor space. If there's enough headroom and your child is 6 or over, a high sleeper is the bigger gain, because the bed goes up and the floor comes back. Under 6, a low cabin bed gives you storage built into the frame with no climbing.
Average rooms
A standard single is the most useful bed you can buy for a growing child, and one with built-in storage replaces a chest of drawers, lasting from the early years into the teens. Our guide to how much storage beds hold compares the options.
Shared rooms
A bunk bed sleeps two in the footprint of one. The top bunk is for children aged 6 and over, and a younger child sleeps on the bottom. If the ceiling is low, look at low bunks; our guide to low bunk beds covers the differences. For three children, a triple bunk works if the room and ceiling allow.
Sleepovers
A bed with a trundle looks like a single and pulls out into two, so it adds a second bed for sleepovers and family visits without taking up extra floor space day to day.
Before you order
- Measure the room, including the ceiling height directly above where the bed will stand.
- Work from the frame dimensions, not the mattress size, and leave space to walk round the bed and open any drawers.
- Check the ladder on any bunk or raised bed, as it isn't always in the headline dimensions.
- Check the maximum mattress depth if it's a raised bed.
- Count the mattresses. A bunk needs two, and one with a trundle needs three.
Not sure? Message us with the room dimensions and your child's age, and we'll tell you what fits.
Common questions
What size bed does a 4-year-old need?
A shorty, small single or standard single all work at a normal, floor-level height. A standard single lasts longest; a shorty fits a small room better.
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 their mattresses aren't interchangeable.
Can I put a standard single mattress on a shorty bed?
No, it's 15cm too long and 15cm too wide. A standard shorty bed needs a shorty mattress, 75 x 175cm. Our own shorty beds are smaller again and take a 70 x 160cm mattress, so check the size on the product page.
What is a European size?
A bed that's 200cm long instead of 190cm. It's common on European-made beds and worth having for a taller child or teenager, and it needs a European mattress to match.
When should my child move to a full-size single?
When there's less than 10cm between their head and the end of the mattress, or they start sleeping diagonally. For children on a shorty or small single, that's often somewhere between 6 and 9.
What mattress depth do I need for a bunk bed?
Check your specific bed, but it's usually 15 or 16cm at most on the top bunk. A deeper mattress lowers the guard rail's effective height.
Is a small double too big for a child?
Not if the room takes it. At 120 x 190cm, it's a good choice for a teenager or a child who has friends to stay. See our guide to small double beds.
Know the size? Find the bed
Shop by size, from shorty beds to doubles.
Single beds Shorty beds Small doublesDeciding on the type of bed rather than the size? Read our kids' bed buying guide.