Choosing the right mattress is just as important as choosing the right bed. The correct size, depth and type can affect your child's comfort, sleep quality and, particularly with raised beds, their safety.

Whether you've just bought a high sleeper, a mid sleeper, a cabin bed or a bunk bed, or you're simply replacing a worn-out mattress, this guide explains everything you need to know before buying.

For general bed-buying advice, see our main Children's Bed Buying Guide.

What Size Mattress Does My Child Need?

Mattress sizes can vary between manufacturers, so always check the exact dimensions of your bed before ordering. That said, most children's beds in the UK use one of the following standard sizes:

• UK single: 90 × 190cm
• European single: 90 × 200cm
• Small double: 120 × 190cm
• Double: 135 × 190cm

Never assume a bed takes a standard UK single mattress just because it's described as a "single bed" — some beds, particularly those from European manufacturers, use the slightly longer European single size instead.

Mattress Depth for Raised Beds

Mattress depth matters far more on a raised bed than on a standard single bed. High sleepers, mid sleepers, cabin beds and bunk beds are all fitted with safety guard rails, and those rails are only effective up to a certain height above the mattress surface.

If the mattress is too deep, it can raise the sleeping surface higher than the guard rail was designed for, reducing its effectiveness and increasing the risk of a child rolling out of bed.

As a general rule:

• Most raised beds require a mattress with a maximum depth of around 15–20cm
• Always check the manufacturer's maximum recommended mattress depth before ordering
• Memory foam and pocket sprung mattresses are often deeper than basic foam mattresses, so measure carefully

Our High Sleeper Bed Safety Guide and Children's Bed Safety Guide cover guard rail safety in more detail.

Mattress Types Explained

There are several common mattress types available for children's beds, each with different characteristics.

Foam Mattresses

Lightweight, affordable and widely used in children's beds. Good for occasional or guest use, and easy for children to handle if a mattress needs to be moved.

Memory Foam Mattresses

Mould to the body for pressure relief and support. Usually deeper than basic foam, so always check depth compatibility with raised beds.

Pocket Sprung Mattresses

Individual springs respond to movement independently, offering good support and breathability. Often a good option for a child's primary everyday mattress.

Open Coil Mattresses

A simpler, more affordable sprung construction. Frequently used for bunk beds because of specific fire safety requirements (see below).

Hybrid Mattresses

Combine springs with foam or fibre layers, aiming to balance support, comfort and breathability.

Mattresses for Bunk Beds

Bunk bed mattresses are subject to additional considerations. Our Are Bunk Beds Safe? guide covers general bunk bed safety, but a few mattress-specific points are worth highlighting:

• Always check the maximum permitted mattress depth for both the top and bottom bunk
• The top bunk mattress must not raise a child above the height the guard rails are designed to contain
• Check the maximum user weight for the top bunk before choosing a mattress
• Look for mattresses that meet current UK fire safety regulations for bunk beds specifically

Our Wooden vs Metal Bunk Beds guide and Best Bunk Bed Buying Guide have more on choosing the right bunk bed overall.

Mattresses for High Sleepers and Mid Sleepers

Because high sleepers and mid sleepers are raised further from the floor, mattress depth and weight both matter.

Consider:

• Maximum mattress depth specified by the manufacturer
• Maximum user weight for the bed
• Whether a heavier memory foam or pocket sprung mattress is manageable to lift into place
• Breathability, since raised beds can sit further from air circulation at floor level

Our What Age Is Safe for a High Sleeper guide covers age and weight guidance in more detail.

Mattresses for Cabin Beds

Cabin beds generally sit closer to the floor than mid sleepers and high sleepers, but many still include guard rails, so the same maximum depth principle applies.

Because cabin beds are popular with younger children, it's also worth checking:

• Firmness suitable for a younger child's developing spine
• Breathable, hypoallergenic fillings where possible
• Whether the mattress meets UK fire safety and general children's bedding standards

Mattresses for Trundle and Sleepover Beds

If your bed includes a pull-out trundle, guest bed or additional sleepover space, check the second mattress requirements separately. Our Beds with Sleepover Beds guide and Day Beds Buying Guide cover this in more depth.

Always check:

• Whether the trundle mattress is included or needs to be purchased separately
• Maximum mattress depth for the trundle to store away correctly
• Trundle mattress size, which can differ from the main mattress

Mattress Firmness for Children

Firmness is partly a matter of personal preference, but there are some general guidelines worth considering:

• Younger children often benefit from a firmer mattress that supports their developing spine
• Teenagers may prefer a softer or medium-firm mattress, similar to an adult preference
• A mattress that is too soft can make it harder for a child to move or get in and out of bed safely, particularly on a raised bed

If in doubt, a medium-firm mattress is generally a safe and comfortable choice for most children.

Mattress Safety Standards

All mattresses sold for use in the UK must meet current fire safety regulations. When buying a mattress, check that it:

• Meets UK fire safety regulations
• Comes with a fire safety label attached (this should never be removed)
• Is suitable for the specific bed type, particularly for bunk beds and raised beds
• Uses breathable materials appropriate for your child's age

See our Children's Bed Safety Guide for wider safety advice when buying a bed and mattress together.

How Often Should You Replace a Child's Mattress?

Most mattresses last around 7–8 years with normal use, although this can vary depending on quality and how the mattress is used.

Signs it may be time to replace a mattress include:

• Visible sagging or lumps
• Springs that can be felt through the surface
• Your child regularly waking up uncomfortable
• The mattress no longer fitting the bed frame correctly
• A change to a larger bed size

What Should You Check Before Buying?

Before ordering a mattress, check:

• Mattress size
• Maximum mattress depth for the bed
• Maximum user weight
• Mattress type
• Firmness
• Fire safety compliance
• Breathability and materials
• Whether the mattress is suitable for bunk beds, if relevant
• Manufacturer's recommended replacement guidance

Mattress Buying Checklist

Before buying, ask yourself:

• Do I know the exact mattress size required?
• Have I checked the maximum mattress depth for the bed?
• Is the bed a bunk bed with specific fire safety requirements?
• Have I checked the maximum user weight?
• Is the firmness suitable for my child's age?
• Does the mattress meet UK fire safety regulations?
• Is a trundle or second mattress required?
• How old is the current mattress being replaced?

Final Thoughts

The right mattress can make just as much difference to your child's sleep as the bed itself. Size and depth are especially important on raised beds, where an oversized mattress can compromise the safety of the guard rails, while firmness and material affect everyday comfort.

If you're still choosing the bed itself, our Children's Bed Buying Guides hub covers every bed type in detail, and our Children's Bed Safety Guide has further advice on keeping your child's bedroom safe as they grow.