Best Mattress for Kids: A UK Guide to Size, Firmness and Age

Choosing a kids mattress is mostly three decisions: the right size for the bed, a firmness that suits a lighter body, and a build that will survive spills, growth spurts and a decade of use. This guide covers each one, by age, with no jargon.

How we put this guide together

We make and sell mattresses, so treat our product picks as exactly that. The sizing, safety and sleep guidance below comes from NHS sources and UK bed standards, and we say clearly where a REM-Fit mattress is not the right choice (cots and toddler beds, and our deeper hybrids on bunk beds).

What kind of mattress does a child need at each age?

A child's needs change more between two and twelve than an adult's do in thirty years. Start with the age, then the bed.

The ages are a guide, not a rule. Many children move into a single earlier, and a tall ten-year-old may already need the room of a small double.

Babies and toddlers: buy a purpose-made mattress

The NHS advice for babies is specific: use a firm, flat mattress and keep the cot clear of pillows, duvets and soft toys. That means a mattress made for the cot it sits in.

We do not make cot or toddler mattresses, and an adult hybrid is not a substitute for one. If your child is still in a cot or cot bed, buy the correct size from a nursery specialist and come back to this guide when they move into a full-size bed.

What size mattress is best for a child?

For a first proper bed, a UK single (90 x 190cm) is the standard choice. It fits almost every children's bed frame sold in the UK and is long enough to last until adulthood.

• Small single (75 x 190cm): useful for box rooms and some cabin beds. Bedding is harder to find.
• Single (90 x 190cm): the default. Widest choice of frames, mattresses and bedding.
• Small double (120 x 190cm): worth considering for teenagers if the room allows it.

Always measure the bed frame before ordering, especially with European frames, which often take a 90 x 200cm mattress. Our UK mattress sizes guide lists every size, and you can browse by size in the single mattress and small double mattress collections.

Bunk beds, cabin beds and high sleepers

This is the one place where a deeper mattress is the wrong choice. The bunk bed safety standard (BS EN 747) requires the guard rail to stand at least 16cm above the top of the mattress, so raised beds have a maximum mattress depth, usually marked on the frame. It is often around 15cm.

What firmness is best for a child?

There is no strong clinical evidence that children need one particular firmness. What matters is that the mattress keeps the spine level and does not let a light body sink into a dip.

Firmness ratings are written with adult weights in mind. A child weighing 25 to 40kg barely compresses a mattress, so every mattress feels firmer to them than it does to you. A very firm adult mattress can feel like a board to a seven-year-old.

For most children a medium or medium-firm mattress is the sensible middle ground: supportive enough as they grow heavier, with enough cushioning at the shoulder and hip for side sleeping. Our mattress firmness guide explains the scale in more detail.

Is pocket sprung or memory foam better for kids?

Either can work. What matters is how the mattress is built, not the label.

With foam, look for a firm, supportive base with a thin comfort layer on top. A deep, soft adult memory foam mattress is a poor fit, because a light child does not weigh enough to make it contour properly. A foam mattress designed for children avoids that, and it is lighter, quieter and shallow enough for raised beds.

Pocket springs add bounce and more airflow, and they suit heavier bodies, so they come into their own for teenagers. The trade-off is depth: most pocket sprung and hybrid mattresses are too deep for a bunk.

Avoid cheap open coil mattresses if the budget allows. They cost less up front but tend to dip sooner, which matters on a mattress you want to last for years.

Our pick for children: the Remy Kidz

The Remy Kidz is the mattress we designed specifically for children. It is a UK single (90 x 190cm), 15cm deep, with a medium-firm feel (7/10): soft on top and supportive underneath.

Remy Kidz Eco Mattress

Designed for growing bodies. Medium-firm (7/10), UK single, 15cm deep, with a removable, machine-washable cover. Good Housekeeping Getting Greener Approved.

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✓ 100-night trial    ✓ 15-year guarantee    ✓ Free UK delivery    ✓ 0% finance

Why it suits children:

• Built in layers for a light body: 25mm of contouring memory foam and 25mm of responsive reflex foam for comfort, over a 100mm supportive base.
• A cover you can wash: the cover zips off and goes in the machine, which matters more on a child's bed than any other.
• 15cm deep: shallow enough for many bunk, cabin and mid sleeper beds. Check the depth marked on your frame.
• Lower-impact materials: made with 75% upcycled foams, with a cover knitted from Seaqual upcycled marine plastic.
• Light to handle: around 15kg, so changing a bunk bed is a one-person job.

The 100-night trial is useful with children, because they cannot tell you much in a showroom. A few weeks of actual sleep will. Delivery on the Remy Kidz currently takes 8 to 12 working days, so order ahead of a room move or a new bed.

For teenagers and bigger beds

The Remy Kidz comes in UK single only. For a teenager, a small single or a small double bed, two of our hybrids are the better fit. Both are 25cm deep, so neither is suitable for a top bunk.

Pocket 1000 Hybrid Mattress

1000 full-height pocket springs with a memory foam comfort layer. Medium-firm (7/10), 25cm deep, Good Housekeeping Winner 2026. Our entry-level hybrid, in single, small double and larger sizes.

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If you need a small single (75 x 190cm), or your teenager sleeps on their side and prefers a softer feel, the 3000 Supreme Hybrid Mattress is medium (6/10) and comes in that size.

Protect it from day one

A child's mattress faces more than an adult's: bedwetting, spilled drinks, illness and the occasional felt tip. Liquid that reaches the mattress is hard to remove, and staining can affect a trial or guarantee.

A washable cover deals with the surface, but it will not stop liquid soaking through. A waterproof, machine-washable protector is the cheapest insurance you can buy. It also keeps skin flakes out of the mattress, which is what dust mites feed on.

Cotton Mattress Protector

Soft jersey cotton over a waterproof membrane that blocks spills, dust mites and allergens. Machine washable, fits mattresses up to 35cm deep, in single and small single sizes.

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If your child sleeps hot, the Tencel Cool version (a Good Housekeeping Winner 2026) is the cooler option. Both are in the mattress protectors collection.

How much sleep do children need?

The mattress matters because children spend so much time on it. NHS guidance on healthy sleep for children recommends:

The teenage figure is from the Newcastle Hospitals NHS children's sleep service. A six-year-old on ten hours a night spends more than 3,600 hours a year in bed.

A mattress will not fix a sleep problem on its own. If your child regularly struggles to fall or stay asleep, speak to your GP or health visitor.

When should you replace a child's mattress?

Replace it when it stops doing its job, whatever its age. The signs are the same as for an adult mattress:

• A visible dip or sag where they sleep
• Springs you can feel through the surface
• They have outgrown it, with feet near the end of the bed
• They wake stiff, or sleep noticeably better in other beds
• Stains or odours that cleaning has not shifted

Be cautious with hand-me-downs. A mattress that already has a body-shaped dip from an older sibling will not support a younger one properly. Our guide on how often to replace a mattress covers lifespan in more detail.

View the Remy Kidz mattress

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