A small double is 120 x 190cm, or 4ft wide. Wider than a single by 30cm and shorter than a standard double by 15cm, which makes it the size that fits a child's bedroom when a full double won't.
As a UK kids' bed specialist, small double is a size we sell a lot of: for teenagers who've outgrown a single, for the bottom bunk of a triple sleeper, and for children who simply sleep better with room to move. Our range runs from £155 to £580, in depths from 10cm to 28cm.
Kids Small Double Mattress Size
Size
Metric (cm)
Imperial (ft/in)
Small double
120 x 190
4ft x 6ft 3in
Continental small double
120 x 200
4ft x 6ft 6in
Single (for comparison)
90 x 190
3ft x 6ft 3in
Double (for comparison)
135 x 190
4ft 6in x 6ft 3in
Small double is also called a 4ft, a three-quarter bed, or occasionally a queen in older British usage. In the US the nearest equivalent is a full or double, though the dimensions differ.
It is not the same as a double. A standard double mattress at 135cm is 15cm too wide for a small double frame and won't fit. This is the most common mistake people make when replacing one.
Continental sizes are 200cm long rather than 190cm. If your bed is a European or Scandinavian design, check which it needs, because a 190cm mattress in a 200cm frame leaves a 10cm gap at the end.
Who a small double suits
A kids small double mattress measures 120cm x 190cm (4ft x 6ft3). It is 30cm wider than a standard UK single mattress and 15cm narrower than a standard double, which makes it a useful in-between size for children and teenagers who need more room than a single in compact bedrooms, shared rooms or guest rooms, but do not have space for a full double. For UK parents choosing a mattress for a child’s bedroom, bunk bed or guest setup in a typical home, getting that size right affects comfort, support, safety and whether the room still works day to day.
The small double size is also sometimes called a queen size or queen size mattress in older UK usage, so it is always worth checking the measurements rather than the name alone.
This guide explains who a small double mattress suits, what to check before you buy, and where people get caught out. It covers the exact size and dimensions, which ages it works best for, whether it is suitable for sharing, bunk bed depth limits, mattress types and firmness, allergy considerations, bed compatibility, ordering advice and the most common questions parents ask when moving a child or teenager up from a single.
Teenagers. The most common reason people buy one. For older children moving up from a 90cm single, the extra width gives solo sleepers or one sleeper more space without taking a full double footprint. In a typical UK bedroom that difference decides whether the room still works.
Children who move a lot in their sleep. Some children simply need the space. A small double often means fewer disturbed nights, fewer trips to reposition someone at 2am, and a better chance of a good night's sleep.
Two children sharing. A small double takes two younger children comfortably, which is why it's the size used on the bottom bunk of a triple sleeper.
Guest and sleepover beds. A small double typically suits one adult, or two smaller people for occasional use, so it works well in guest rooms and for sleepovers without taking over the room the rest of the time.
Parents reading at bedtime. Worth saying, because it's a real reason. A small double means you can lie down alongside rather than perch on the edge. By comparison, a single mattress gives you 30cm less width, so it can feel restrictive very quickly.
A useful rule on length: aim for a mattress at least 10cm longer than your child is tall. At 190cm a small double comfortably takes someone up to about 180cm, and the continental 200cm version takes a taller teenager. Once there's less than 10cm between the top of their head and the end of the mattress, you've roughly a year left in it.
The bit most retailers don't mention: depth
If the small double mattress is going on the bottom bunk of a triple sleeper or other bunk beds with guard rails, there's a maximum depth. It's usually 15 or 16cm.
Guard rails are designed to sit a set height above the mattress surface. Bunk bed mattresses must also fit securely within the bed frame, not just sit below the rail height. Most small double mattresses on the high street are 20cm or deeper, and putting one on a raised or railed bed removes that clearance and stops the rail doing its job.
Our 15cm range comes in small double specifically for this. On a normal floor-level bed frame there's no limit, and a deeper mattress may suit a heavier body better.
Trundles are shallower again, usually around 10cm, so the mattress clears the frame above when it slides away.
Small double mattresses for children and teenagers
For bunks, triple sleepers and railed beds — 15cm
ComfortSleep 15 — £189.99
Reflex foam. Firm, supportive and the most affordable of the three. Good for younger children and lighter body weights, though it is not automatically the best mattress for every child because the right choice depends on age, weight, and bed type. Available in small double and continental small double.
MemoryDream 15 — £246.99
A memory foam mattress over a reflex base. Contours to the body and it's quiet, which matters if someone is sleeping underneath, and it can suit a child depending on their preferred sleeping position. Small double and continental small double.
PocketRest 15 — £274.99
Pocket spring support, so more airflow, better temperature regulation and a cooler sleep. The one to choose for a child who runs hot, with support that can offer superior support and promote healthy spine alignment for kids. Small double and continental small double.
Some mattresses in this 15cm range are available vacuum-packed for easy transport.
For trundles and pull-out beds — 10cm
TrundleEase 10 — £155.00
Built at 10cm so it clears the frame above when the trundle slides back. Small double and continental small double.
For teenagers on a normal bed frame — 18cm
MemoryTeen 18 — £299.00
A deeper mattress and memory foam mattress, built for a heavier and taller person, with a feel better suited to an older child or teenager. Not suitable for a bunk or railed bed, since it exceeds the guard rail clearance, but the better choice on a floor-level frame.
Sprung and memory foam options
Guardian Orthopaedic Sprung Mattress — £215.00
A firmer spring mattress in the traditional orthopaedic style, with a sturdier feel and more support.
Florence Memory Sprung Mattress — £250.00
A hybrid mattress with spring support and memory foam comfort layers over the top.
Pippa Pocket Sprung Mattress — £295.00
Like many pocket sprung mattresses, it uses individually wrapped springs for more targeted support and can offer exceptional comfort.
If you're comparing mattress type options, note that open coil mattresses use continuous wire for firmer support, while a pocket spring build is often chosen for superior support.
Natural and wool
Little Folks Open Coil Small Double Mattress — £304.99
Little Folks Wool Pocket Sprung Small Double Mattress — £579.99
Good options if your little one sleeps warm or has sensitivities.
Natural wool fillings, pocket sprung; the premium option in the range, made with premium materials and breathable materials that help if a child gets too warm overnight, while natural, hypoallergenic fillings can help prevent dust mites from accumulating. In pocket sprung designs, different filling types can also change the warmth and overall feel. Latex mattresses are durable and breathable, often lasting over 10 years.
Full depth small double mattresses
For an older teenager or an adult on a normal bed frame, where depth isn't restricted, the right new mattress is usually a full-depth option for better comfort under a heavier body weight and a better sleep experience; these are all our mattresses for normal bed frames in this category. Next day delivery is available on selected small double mattresses, and you can choose a preferred delivery date. Old mattress removal can be added if needed.
- QuiltRest 23 — £229.00, quilted, 23cm
- OrthoSupport 24 — £299.00, firmer orthopaedic support, 24cm
- MemorySupport 25 — £349.00, memory foam, 25cm
- PocketBalance 26 — £399.00, pocket sprung, 26cm
- NaturalLoft 27 — £429.00, natural fillings, 27cm
- VitalRest 28 — £449.00, our deepest, 28cm
Which type?
TypeFeelBest for
Reflex foamFirm, supportiveYounger children, guest beds, tighter budgets
Memory foam mattressContouring, quietRestless sleepers, most children and teenagers
Pocket sprungTraditional, some bounceAnyone who sleeps hot
Open coilFirmer, more affordableA spring mattress option for occasional use
Natural woolBreathable, temperature regulatingSensitive sleepers, all-year comfort
For a child or teenager, medium to medium-firm is generally right, though a firmer mattress can work for some children and teenagers, not all. Too soft lets the hips sink and the spine curve. Too firm creates pressure points at the shoulder and hip. The best mattress firmness depends on sleeping position and build, with side sleepers often needing more pressure relief at the shoulder and hip. Comfort grades also vary by mattress type, including foam mattress, pocket sprung, and hybrid mattress options. A medium firm mattress is ideal for guest rooms. The best firmness also depends on sleeping position and what feels most comfortable, and a pocket sprung option can be a strong choice if you want more responsive support.
Allergies and breathability
If your child has asthma, eczema or a dust mite allergy, here’s some practical advice: focus first on a washable cover and a protector you can put through the machine. Hypoallergenic mattresses and fillings can help reduce allergy symptoms in children and protect against common triggers. Most allergens accumulate in the top few centimetres, so what you can wash is what you can control. Look for mattresses certified to reduce allergens like dust mites.
Beyond that, breathability helps. A mattress that moves moisture away rather than holding it stays fresher between washes, and pocket sprung constructions allow more airflow through the mattress than solid foam does. OEKO-TEX certification indicates textiles are free from harmful chemical emissions.
See our hypoallergenic mattresses, and the Bamboo Mattress Protector in small double at £35, which is breathable rather than plastic-backed so it doesn't trap heat the way a standard waterproof protector does.
Beds that take a small double
If you're buying the bed as well, start with a small double bed frame or compare:
The mattress size each bed requires is stated on its product page. Work from that rather than measuring the frame, since the frame is always larger than the mattress.
Before you order
- Confirm it's a small double, not a double. 120cm wide, not 135cm. Measure the frame if you're unsure.
- Check the length. 190cm standard, 200cm continental.
- Check the maximum depth if the bed has guard rails or is a bunk. Usually 15 or 16cm.
- Add a protector. The main reason children's mattresses get replaced early is what's happened to them, not wear, especially after night-time accidents; water-repellent protection helps with cleaning after them, which matters even more if the bed is for a toddler moving up to a larger size.
- Need it quickly? Selected small double mattresses are available with next day delivery.
- Pick a slot that suits you. You can schedule your new mattress to a preferred delivery date.
- Allow 24 to 48 hours for a rolled mattress to fully expand after unwrapping.
- Replacing an old one too? Old mattress removal can be added for £39 at checkout.
Not sure? Message us with the bed you have and we'll tell you which size and depth it needs.
Small Double Mattresses: Common Questions
What size is a small double mattress?
120 x 190cm, or 4ft x 6ft3. A continental small double is 120 x 200cm. This size mattress is sometimes called a queen size mattress in older UK usage.
Will a double mattress fit a small double bed?
No. A standard double is 135cm wide, which is 15cm too wide for a small double frame.
Is a small double big enough for a child?
Comfortably. It's 30cm wider than a single, and it's the size most families move a teenager up to when a single starts feeling narrow, while also suiting solo sleepers who want more space for a restful night's sleep.
Can two children share a small double?
Two younger children, yes. It's the size used on the bottom bunk of most triple sleepers for exactly that reason.
What depth small double mattress for a bunk bed?
Usually a maximum of 15 or 16cm, so the guard rails stay effective. Check the figure on your bed's product page. On a normal floor-level frame there's no limit.
What's the difference between small double and continental small double?
Length. Small double is 190cm, continental is 200cm. Both are 120cm wide, and they aren't interchangeable.
What's the best small double mattress for a child?
The best mattress depends on your child's age, bed type, mattress type and support needs. On a bunk or railed bed, one of our 15cm range. On a normal frame, MemoryTeen 18 or deeper for a teenager, with mattress firmness affecting the right feel and support. The right support level helps keep them comfortable night long. Some spring-based designs use an open coil spring system.
Is a small double the same as a 4ft?
Yes. Small double, 4ft and three-quarter bed all describe 120 x 190cm.
Is a small double the same as a king size mattress or super king?
No. Both are larger sizes, so they won't match a small double bed frame.
Firm or soft for a growing child?
Medium to medium-firm. The right firmness should match your child's build and sleeping habits, because a mattress that's too soft doesn't properly support a spine that's still developing.
Do you sell small double mattress protectors?
Yes. Our Bamboo Mattress Protector comes in small double at £35, and it's breathable rather than plastic-backed, so it doesn't trap heat and helps keep the bed cleaner through the night.
What is a small double mattress topper?
A small double mattress topper is an extra comfort layer that sits on top of the bed, and it must match the mattress dimensions for a proper fit.
Are hypoallergenic mattresses worth considering for children?
Yes, especially for sensitive sleepers. Hypoallergenic fillings help protect children with allergies and can be worth considering if your child is prone to irritation.
How often should a child's mattress be replaced?
Every five to seven years, or sooner if outgrown or damaged. More in our guide to how often to change a mattress.
Can a small double work for younger kids as well as teenagers?
Yes. For younger children it gives extra room to stretch out or share occasionally, and it also works well in compact rooms, while for older children it feels less restrictive than a single and can even suit adults for guest use.
Browse our full kids' mattress range, or read the kids' mattress guide for every size and depth.
