How To Choose a Mattress For Kids

As Head of Sleep Science here at Mattress Online, I’m often asked how to pick the right mattress for kids. Sleep plays a vital role in their growth and development, and the right mattress can make all the difference.

In this guide, I’ll walk you through what to look for, when to switch mattresses, and how to choose a kids mattress that meets your child’s needs as they grow.

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The importance of sleep for children

Children need around 10-14 hours of sleep a night, depending on their age, and that sleep is essential for both mental and physical development. To get the right rest, they need a healthy balance of light and deep sleep.

• Light sleep supports learning and emotional processing
• Deep sleep is when the body grows and repairs, releasing essential growth hormones

To help your child get the most from each stage of sleep, their mattress needs to be comfortable, safe, and properly supportive.

A good kids mattress should:

• Provide a comfortable sleep environment
• Support their growing body
• Offer a clean, breathable surface

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When should my baby move to a child’s mattress?

Most babies outgrow their cot mattress between 18 and 36 months. If the cot’s feeling cramped or they’re starting to climb out, it’s usually a good sign they’re ready to upsize.

But every child is different - it’s all about watching for those signs and moving when the time feels right.

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What size mattress does a child need?

When choosing a mattress size for your little one, it’s not just about your child’s current height  - think ahead to how much they’ll grow and how long you want the mattress to last. 

You’ll also need to factor in:

• The space available in their room
• The bed frame they’re moving into (or one you’re planning to buy)
• How easy it is for them to get in and out of bed on their own

Children’s mattresses usually come in the following sizes:

Size	Metric	Imperial
Single	90cm x 190cm	3' x 6'3"
Small Double	120cm x 190cm	4' x 6'3"
Double	135cm x 190cm	4'6" x 6'3"

You can use a standard single mattress and bed for your child, but it’s worth noting that these are designed for adults.

Children’s mattresses and beds are often shallower, which makes it easier for little legs to get in and out of bed safely.

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Types of children's mattresses

As with adult mattresses, children’s mattresses come in a range of support and comfort layer options.

When helping parents choose, I always recommend thinking about your child’s age, sleep habits, and any allergies or sensitivities.

Here’s a quick breakdown of the main types:

Support core options

Standard sprung (open coil)

A great entry-level choice. Standard sprung kids mattresses use interconnected springs to spread weight evenly and offer good support for your child.

Pocket sprung

Each spring moves independently to adapt to your child’s shape and movement while they sleep. I recommend pocket sprung mattresses for older children who need more tailored support as they grow.

Foam

Foam mattresses are soft and offer excellent pressure relief, making them a great option for a child’s first ‘big bed’. 

Just keep in mind that they can retain heat and take longer to dry after accidents or spills. They’re also more likely to be chemically treated, so they may not be the best choice for children with allergies or sensitivities.

Comfort layer options

Fibre layers

There are two main types of fibre comfort layer options in kids mattresses:

• Polyester fibres are breathable and quick-drying, helping to keep your kid cool and comfortable through the night.
• Natural fibres like wool also regulate temperature effectively, making them a great option for children who struggle to stay at a comfortable temperature while they sleep.

Fibre mattresses often require fewer chemical treatments, as materials like wool are naturally flame-retardant, making them a more natural choice for your child.

Foam layers

Foam is a popular comfort layer thanks to its pressure-relieving qualities, and it comes in several types:

• Memory foam moulds your child’s body and reduces pressure points. It’s very comfortable but can retain heat.
• Gel foam offers similar comfort but is more breathable, helping your child stay cooler at night.
• Reflex foam is firmer than memory foam and provides a solid surface without the ‘sinking in’ feeling.

Ultimately, the right mattress balances comfort, support, and practicality, giving your child the best chance at a healthy night’s sleep.

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Choosing a mattress for a bunk bed

If you’re buying a mattress for your child’s bunk bed, depth is key for safety. According to safety standard BS EN 747-1:2012+A1:2015, the mattress must allow for proper guardrail coverage to help prevent falls.

Here's what the standard requires:

• The safety barrier must be at least 26cm above the upper surface of the bed base
• The top of the mattress must sit at least 16cm below the top edge of the safety barrier
• The maximum thickness of the mattress should be clearly marked on the bed frame

This means that in many cases, a mattress no thicker than 10cm is safest, especially if the guardrails are only 26cm high. Always check your specific bunk bed’s measurements before buying a mattress.

Bunk bed mattresses are made from the same materials as standard kids mattresses, but they’re specially designed with these safety requirements in mind.

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Can my child use a second-hand mattress?

Passing down a mattress between siblings and family members can seem like a practical option, especially when kids outgrow things so quickly. But before you reuse a mattress, there are a few important things to consider.

1. Is it still supportive?

A mattress should support your child’s posture and growing body. Ask yourself:

• Can your child feel the bed base through the mattress?
• Is their spine misaligned when they lie on their side?
• Is the surface sagging or uneven?

If the answer to any of these is yes, it’s time for a new one.

2. Is it hygienic?

If the mattress is from your own home and has been properly protected, it may still be clean enough to reuse. But if it comes from elsewhere, consider:

• Has it been heavily used?
• Was a waterproof mattress protector used?
• Has it been exposed to accidents or spills?
• Does it look generally unclean and unkempt?

If you wouldn’t sleep on it yourself, it’s probably not right for your child either.

3. Is it safe?

Always check the condition of the mattress before using it. Look out for:

• Broken or exposed springs
• Tears, holes, or frayed fabric
• Sagging, dips, or uneven areas
• Missing safety labels or non-compliance with current fire regulations

A damaged mattress isn’t just uncomfortable — it can be unsafe. If in doubt, it’s always better to replace it.

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How often should I replace my child's mattress?

There’s no fixed rule for when to replace a kids mattress, it depends on their age, how they sleep, and how well the mattress has held up. 

But as a general guide, here’s what I recommend:

Child’s age	Replace their mattress every
3–10 years old	3 years
10–16 years old	5 years

This is largely down to how quickly children grow and develop during these years. Even with protective covers, accidents and wear can affect how well their mattress supports them.

Think it’s time to replace your child’s mattress? Check for:

• Sagging or lumps
• Springs poking through
• Spills or stains that won’t come out
• Signs your child isn’t sleeping well or wakes up uncomfortable

Every child is different, so use your judgment. If the mattress no longer looks or feels right, it’s probably time for a new one.

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I hope this guide has helped you feel more confident about choosing a mattress that supports your child’s growth, comfort, and development. Whether they’re moving into their first ‘big bed’ or simply need an upgrade, the right mattress can make all the difference to how well they sleep - and how well they grow.

At Mattress Online, we’ve got a handpicked range of children’s mattresses designed with safety, support, and quality sleep in mind.

Explore our kids’ mattresses now and find the perfect fit for your growing sleeper.

Need more sleep tips? Visit The Sleep Journal for expert advice on everything from bedtime routines to creating a sleep-friendly space.