The short answer
Plan on replacing a child's mattress every 5 to 7 years, and expect at least one replacement to be driven by size rather than age. The 7 to 10 years you'll see quoted elsewhere is written about adult mattresses.
Almost every guide on this subject is about adult mattresses, where the limit is the foam or springs wearing out. Children's mattresses rarely get that far. They're outgrown, damaged or heavily soiled long before they wear out, so they need a different timetable. This guide covers why, the signs a mattress needs changing, the size changes to plan for, and how to make one last.
On this page
Why children's mattresses are different
They get outgrown
A cot bed mattress is 140cm long, a shorty 175cm and a single 190cm. Most children move through at least two, and the trigger is height, not wear.
They take more punishment
Accidents, spilled drinks, illness, and years of being used as a trampoline. Even with a protector, a child's mattress absorbs far more than an adult's.
Growing bodies need support
A mattress that has gone soft in the middle isn't just uncomfortable. It stops supporting a spine that's still developing.
They get handed down
Sensible with a bed frame, less so with a mattress that has already done six or seven years with an older sibling.
Signs it needs replacing
Check the mattress itself rather than going by the date. Strip the bed, look at it in daylight, and press down across the whole surface.
- A dip that doesn't recover within a minute or two of getting up.
- Lumps, or springs you can feel through the surface.
- Edges that collapse, so sitting on the side feels like it's giving way.
- Stains or a smell that survive a proper clean.
- Your child says it's uncomfortable, or keeps waking stiff or achy with no other explanation. Children rarely complain about a bed unless something is wrong with it.
Any two of those together, and it's time, whatever the age of the mattress.
Size changes: the ones people plan badly
These catch families out because they arrive faster than expected.
| Stage | Mattress | Typically |
|---|---|---|
| Cot bed or toddler bed | 70 x 140cm | Up to about 4 or 5 |
| Shorty | 75 x 175cm | Roughly 3 to 8, in a smaller room |
| Single | 90 x 190cm | From about 3 or 4 into the teens |
| Continental single | 90 x 200cm | Tall children and teenagers |
The 10cm rule. With your child lying flat and their head at the top of the mattress, measure the space between their feet and the end. Once there's less than 10cm, they have roughly a year left in it.
The step most people skip is the shorty. It's useful in a small room and buys a few years, but it means an extra mattress along the way, so if space allows, going straight from a cot bed to a single saves a purchase. We stock shorty mattresses in the correct 75 x 175cm size, which many retailers don't. Our kids' bed size guide covers every size.
Bunk beds and high sleepers: check the depth
This is the most expensive mistake we see, and it happens most often at replacement time rather than when the bed is bought.
Raised beds have a maximum mattress depth, usually 15 or 16cm. Guard rails are designed to sit a set height above the mattress surface. A 20cm mattress, which is what most high-street singles are, takes 5cm or more off the rail's effective height. The rail is still there, but it isn't doing its job.
- Replace both bunk mattresses at once. Two mattresses of different ages means one child on a good bed and one on a worn one. Buying together is simpler and fairer.
- Trundles have their own limit, usually around 10cm, so the mattress slides under the bed above. A standard mattress won't fit; the TrundleEase 10 is made for this.
Our bunk bed mattress guide covers depths and sizes in more detail.
What to replace it with
For a child, the choice is simpler than the adult market makes it look. Our own range is made in the UK, arrives vacuum packed and rolled so it comes upstairs easily, and our 15cm mattresses are made for bunk beds and high sleepers.
Memory foam, 15cm
MemoryDream 15
Contours to the body, good for restless sleepers, and quiet. Runs slightly warmer than springs. The one most parents choose.
Sizes and details
Pocket sprung, 15cm
PocketRest 15
More airflow, so it sleeps cooler, with a traditional feel and a little bounce. Better for a child who sleeps hot.
Sizes and details
Reflex foam, 15cm
ComfortSleep 15
Supportive, with a medium feel, and our best-value option. Good for younger children and beds that don't get nightly use.
Sizes and detailsFor an older child or teenager on a bed without guard rails, where the depth limit doesn't apply, the MemoryTeen 18 is deeper, at 18cm. For bedwetting, the DryComfort 15 is fully waterproof. Our guide to the best single mattress for kids compares them.
Making one last longer
- Use a protector from day one. It's the biggest single factor in how long a child's mattress lasts, and a waterproof protector costs a fraction of a new mattress.
- 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.
- Air it regularly. Pull the bedding back for an hour before making the bed.
- Deal with accidents the same day. Once urine dries in, the smell is far harder to remove. Our guide to removing urine smell from a mattress covers what works, and our mattress cleaning guide covers everything else.
- Check the base. A broken slat or sagging base will ruin a new mattress within months, and it's often the real cause when one seems to fail early.
Common questions
How often should a child's mattress be replaced?
Every 5 to 7 years, or sooner if it has been outgrown, damaged or repeatedly soiled. The 7 to 10 years you'll see elsewhere is written about adult mattresses.
Can I pass a mattress down to a younger sibling?
If it's in good condition and only a few years old, yes. If it has already done six or seven years, or been through accidents, you'd be giving the younger child a mattress near the end of its life. Check it properly rather than assuming.
My child's feet are near the end of the bed. How long have I got?
Roughly a year once there's less than 10cm of space beyond their feet. Plan the next size now rather than waiting for it to become urgent.
Can I use any single mattress on a bunk bed?
No. Check the maximum depth for your bed, usually 15 or 16cm. Most standard singles are 20cm or more, which lowers the guard rail's effective height.
Does a mattress protector really extend its life?
Considerably, on a child's bed. Most children's mattresses are replaced because of what has happened to them rather than because the foam has worn out, and a protector stops spills and accidents soaking in. It won't fix a mattress that has already sagged.
How do I dispose of an old mattress?
Most councils collect bulky waste for a fee, and many household waste recycling centres take mattresses. Book it before the new one arrives so you're not storing both.
Time for a new one?
UK-made kids' mattresses in every size, including 15cm for bunk beds and high sleepers.
Shop kids' mattressesNot sure which size? Read our kids' mattress size guide.
