Mattress size names sound official, but they are not quite. The National Bed Federation (NBF), the trade body for UK bed makers, publishes the standard sizes below — and also warns that "bed sizes are not standardised": a king from one maker may not match a king from another, especially when the mattress and base come from different companies. So always check the measurements in centimetres.
The standard UK sizes
All six are drawn below at the same scale, so you can see how much room each step up really adds.
| Size | Centimetres | Feet and inches |
|---|---|---|
| Small single | 75 × 190cm | 2'6" × 6'3" |
| Single | 90 × 190cm | 3' × 6'3" |
| Small double | 120 × 190cm | 4' × 6'3" |
| Double | 135 × 190cm | 4'6" × 6'3" |
| King | 150 × 200cm | 5' × 6'6" |
| Super king | 180 × 200cm | 6' × 6'6" |
Sizes as published by the NBF's Bed Advice UK site.
Which size suits you?
- Small single — the NBF describes it as mainly for younger children and "a good 'first' bed when moving from a cot".
- Single — suits children and adults, and is the most common size for a child's bed.
- Small double — plenty of room for one adult but "a little cramped with two", says the NBF. It is also called a three-quarter bed (or sometimes a queen).
- Double — the NBF points out that a 135cm double gives each of two sleepers about 67.5cm (2'3") — "the same space a baby has in a cot".
- King — 15cm wider and 10cm longer than a double.
- Super king — the same length as a king and 30cm wider; the NBF says it is only suitable for larger bedrooms.
Length: at least 10cm longer than the tallest sleeper
The NBF advises a bed "at least 10cm longer than the tallest person". UK singles and doubles are 190cm long, so it suggests anyone taller than 5'11" (180cm) looks at a 200cm-long king or super king. Some makers produce beds up to 215cm long.
Width: the elbow test
When you try a bed for two, the NBF suggests lying side by side on your backs with your hands behind your heads and elbows out. If your elbows don't touch, there is enough room.
Cot and cot bed sizes
Cot mattresses are usually 60 × 120cm and cot bed mattresses 70 × 140cm — the sizes UK makers such as Silentnight and IKEA sell. What matters most is the fit: The Lullaby Trust says a baby's mattress should fit the cot properly, with no gaps. Measure the inside of the cot rather than relying on the label.
EU sizes are different
Many beds sold in the UK — including most IKEA bunk and loft beds — take European mattress sizes such as 90 × 200cm, 140 × 200cm and 160 × 200cm. A UK single (90 × 190cm) on a 90 × 200cm frame leaves a 10cm gap at the foot; a UK double is 5cm narrower and 10cm shorter than an EU 140 × 200.
Bigger than super king
Some makers sell larger sizes. Hypnos, for example, lists an emperor mattress at 200 × 200cm.
US names
Hypnos notes that a US queen is close to a UK king (150 × 200cm) and a US king is close to a UK super king (180 × 200cm) — worth knowing if you are reading American reviews.
Related guide: Choosing mattress firmness by sleeping position