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.
Small double mattress size
SizeMetricImperialSmall double120 x 190cm4ft x 6ft3Continental small double120 x 200cm4ft x 6ft6Single (for comparison)90 x 190cm3ft x 6ft3Double (for comparison)135 x 190cm4ft6 x 6ft3
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
Teenagers. The most common reason people buy one. A 90cm single starts to feel narrow somewhere around thirteen, and a small double gives 30cm more width without the 15cm a full double would add. 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 and fewer trips to reposition someone at 2am.
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. Wide enough for an adult, narrow enough not to dominate a child's 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.
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 on any bed 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. 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 deeper is generally more comfortable for a heavier body.
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. Available in small double and continental small double.
MemoryDream 15 — £246.99
Memory foam over a reflex base. Contours to the body and it's quiet, which matters if someone is sleeping underneath. Small double and continental small double.
PocketRest 15 — £274.99
Pocket springs, so more airflow and a cooler sleep. The one to choose for a child who runs hot. Small double and continental small double.
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
Deeper memory foam, built for a heavier and taller body. 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 options
Guardian Orthopaedic Sprung Mattress — £215.00
Firmer sprung support in the traditional orthopaedic style.
Florence Memory Sprung Mattress — £250.00
Springs with a memory foam layer over the top.
Pippa Pocket Sprung Mattress — £295.00
Individually pocketed springs for more targeted support.
Natural and wool
Little Folks Open Coil Small Double Mattress — £304.99
Little Folks Wool Pocket Sprung Small Double Mattress — £579.99
Natural wool fillings, pocket sprung. The premium option in the range.
Full depth small double mattresses
For an older teenager or an adult on a normal bed frame, where depth isn't restricted. More filling means more comfort under a heavier body weight.
- 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 forReflex foamFirm, supportiveYounger children, guest beds, tighter budgetsMemory foamContouring, quietRestless sleepers, most children and teenagersPocket sprungTraditional, some bounceAnyone who sleeps hotOpen coilFirmer, more affordableOccasional and guest useNatural woolBreathable, temperature regulatingSensitive sleepers, all-year comfort
For a child or teenager, medium to medium-firm is generally right. Too soft lets the hips sink and the spine curve. Too firm creates pressure points at the shoulder and hip. Firmer is the safer error of the two on a growing body.
Allergies and breathability
If your child has asthma, eczema or a dust mite allergy, two things matter more than the mattress material itself: a washable cover and a protector you can put through the machine. Most allergens accumulate in the top few centimetres, so what you can wash is what you can control.
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.
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:
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.
- Allow 24 to 48 hours for a rolled mattress to fully expand after unwrapping.
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.
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.
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?
Medium to medium-firm. On a bunk or railed bed, one of our 15cm range. On a normal frame, MemoryTeen 18 or deeper for a teenager.
Is a small double the same as a 4ft?
Yes. Small double, 4ft and three-quarter bed all describe 120 x 190cm.
Firm or soft for a growing child?
Medium to medium-firm. 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.
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.
Browse our full kids' mattress range, or read the kids' mattress guide for every size and depth.
