Buying a mattress for a bunk bed is not the same as buying one for a normal bed. There's a maximum depth, you need more than one, and if there's a trundle the third one is different again.
Get any of it wrong and it either doesn't fit or it compromises the guard rail. Here's everything in one place.
1. Depth is a safety figure, not a preference
The top bunk of a bunk bed takes a maximum mattress depth, usually 15 or 16cm.
Guard rails are designed to sit a set height above the mattress surface. That gap is what stops a child rolling over the rail. Most high-street single mattresses are 20cm or deeper, so putting one on a bunk removes 5cm of effective rail height.
The rail is still there. It just isn't doing what it was designed to do.
Check your bed's stated maximum before ordering anything. It's on the product page, and it varies between models because the bed manufacturer sets it based on their rail height.
The bottom bunk is different
There's no rail above the bottom bunk, so no depth restriction in most cases. You can go deeper for comfort if you want to.
In practice most families buy two identical mattresses, which is simpler and means the children aren't sleeping on noticeably different beds.
Trundles are different again
A trundle mattress has to clear the underside of the bottom bunk when it slides away. That usually means around 10cm, and a standard mattress physically won't fit.
2. How many do you need?
| Bed | Mattresses |
|---|---|
| Standard bunk bed | 2, both within the top bunk's depth limit |
| Bunk with a trundle | 3 — two at 15cm, one at 10cm |
| Triple bunk | 3 |
| Family bunk, double bottom | 2 — a small double and a single |
| Family bunk with trundle | 3 |
| Quadruple bunk | 4 |
This is the most commonly forgotten part of a bunk bed order. A bed arrives, gets built, and there's nothing to sleep on.
3. Which size?
Most bunk beds take a standard UK single at 90 x 190cm. Three exceptions worth knowing:
- Shorty bunks take 75 x 175cm. A standard single is 15cm too long and won't fit.
- Continental bunks take 90 x 200cm. A 190cm mattress leaves a gap at the end, which is uncomfortable and an entrapment risk on a raised bed.
- Family bunks usually take a small double at 120 x 190cm on the bottom and a single on top.
The bed's product page states the mattress size it needs. Work from that rather than measuring the frame, since the frame is always larger than the mattress.
4. Our 15cm range
All made in the UK, all built to 15cm specifically for bunk beds and high sleepers, all vacuum packed and rolled so they come up a ladder easily.
ComfortSleep 15 — from £160
Reflex foam. Firm and supportive, and the most affordable of the three. Good for younger children, lighter body weights, and the bottom bunk of a bed that gets occasional use.
Eight sizes, from shorty to continental double.
MemoryDream 15 — from £220
Memory foam over a reflex base. Contours to the body and it's quiet, which matters more on a bunk than people expect: a sprung mattress on the top bunk can be heard from the bottom one.
Eight sizes, from shorty to continental double.
PocketRest 15 — from £230
Pocket springs. More airflow, so it sleeps cooler. Worth considering for the top bunk specifically, since heat rises and the top bunk runs two to three degrees warmer than the bottom.
Single, continental single, small double, double.
TrundleEase 10 — from £130
Built at 10cm for pull-out and trundle beds. This is the one that clears the frame when the trundle slides back.
Eight sizes, from shorty to continental double.
See the full bunk bed mattress range →
5. Should the two mattresses be the same?
Usually yes, and for a practical reason as much as a fair one: children swap bunks. If one mattress is noticeably better than the other, you'll hear about it.
Where it's worth differing:
- Top bunk sleeps hot. A pocket sprung mattress on top and foam underneath is a reasonable split.
- Big age gap. A firmer mattress suits a younger, lighter child; a teenager on the bottom bunk may want something different.
- Budget. If the bottom bunk is mostly for occasional sleepovers, a ComfortSleep underneath and a MemoryDream on top is a sensible way to split the spend.
6. Things that catch people out
Buying one mattress. The bed listing price almost never includes them, and it's two, or three with a trundle.
Assuming a standard single fits a shorty. It's 15cm too long.
Using a supermarket mattress on the top bunk. Almost all are 20cm or more.
A standard mattress on a trundle. It won't slide away, and you'll only find out once it's unrolled.
Forgetting the protector. Cleaning a mattress on a top bunk is genuinely difficult, and it's the one place where preventing a spill matters most. Take the mattress down to the floor rather than trying to clean it in place.
7. Getting it up there
A rolled mattress is far easier to carry upstairs and lift onto a top bunk than a conventional one. Unroll it on the bunk rather than on the floor.
Allow 24 to 48 hours for it to fully expand before making the bed. It'll look thinner than expected for the first few hours.
Before you order
- Check the maximum depth on your bed's product page.
- Check the mattress size the bed requires.
- Count them. Two, or three with a trundle.
- Add protectors. Cheaper than replacing a mattress, and much easier than cleaning one at height.
- Order with the bed so everything arrives together.
Common questions
What depth mattress for a bunk bed?
Usually a 15 or 16cm maximum on the top bunk. Check your bed's product page for the exact figure.
Why does bunk bed mattress depth matter?
Guard rails sit a set height above the mattress surface. A deeper mattress reduces that clearance and the rail becomes less effective.
Can I use a thicker mattress on the bottom bunk?
Usually yes, since there's no guard rail above it. Most people buy two identical ones anyway.
What size mattress does a bunk bed take?
Most take a standard UK single at 90 x 190cm. Shorty bunks take 75 x 175cm and continental bunks take 90 x 200cm.
How many mattresses do I need for a bunk bed?
Two. Three if it has a trundle, and the trundle one is shallower at around 10cm.
What mattress fits a trundle bed?
Around 10cm deep, so it clears the frame above when it slides away. A standard mattress won't fit.
Foam or sprung for a bunk bed?
Foam is quieter, which matters when someone is sleeping underneath. Sprung is cooler, which matters more on the top bunk. Either works.
Are 15cm mattresses comfortable enough?
Yes, for a child. Depth and comfort aren't the same thing, and a well-made 15cm mattress supports a child's weight perfectly well. The extra depth in an adult mattress is there for adult body weight.
Buying the bed too? Read our bunk bed buying guide, or browse all bunk beds.
