Why UK and US beds do not match
Bed sizes grew up separately in each country, from different furniture traditions and different standard bedstead widths, so there was never a shared table to align them. The result is a set of near-misses: a UK double is 135 cm wide while a US full (also called a double) is 137 cm wide — close enough to look interchangeable, different enough that fitted sheets and frames do not swap cleanly. Lengths diverge more: UK beds are usually 190 cm long, or 200 cm for king and super king, while US beds run 191 cm (75 inches) or 203 cm (80 inches), and California king stretches to 213 cm (84 inches). Depth is the wild card everywhere: mattress depths vary by brand and model, typically from about 20 cm to 35 cm, so depth is never part of the size name.
UK mattress sizes (typical)
All UK figures below are the typical standard dimensions in centimetres; lengths are 190 cm except king and super king at 200 cm. Some brands also sell a small single (75 × 190 cm) and a small double is sometimes called a three-quarter bed.
| UK size | Width (cm) | Length (cm) | Width (in, approx) | Length (in, approx) |
|---|---|---|---|---|
| Single | 90 | 190 | 35 | 75 |
| Small double | 120 | 190 | 47 | 75 |
| Double | 135 | 190 | 53 | 75 |
| King | 150 | 200 | 59 | 79 |
| Super king | 180 | 200 | 71 | 79 |
US mattress sizes (typical)
US sizes are defined in inches; centimetre figures below are those inch dimensions converted (1 inch = 2.54 cm) and rounded. Twin XL exists because college dorm beds needed extra length for taller students, and California king exists because the standard king's width was too much for some bedrooms — both are reminders that US sizes answer local problems, not a global system.
| US size | Width (in) | Length (in) | Width (cm) | Length (cm) |
|---|---|---|---|---|
| Twin | 38 | 75 | 97 | 191 |
| Twin XL | 38 | 80 | 97 | 203 |
| Full / Double | 54 | 75 | 137 | 191 |
| Queen | 60 | 80 | 152 | 203 |
| King | 76 | 80 | 193 | 203 |
| California king | 72 | 84 | 183 | 213 |
Near-equivalents that still do not swap
UK single (90 × 190 cm) is close to US twin (97 × 191 cm) but 7 cm narrower; UK double (135 × 190 cm) is close to US full (137 × 191 cm) and is the safest cross-Atlantic pairing, differing by only 2 cm in width and 1 cm in length; UK king (150 × 200 cm) is close to US queen (152 × 203 cm) but 3 cm shorter. UK super king (180 × 200 cm) has no US equivalent at all — it sits between US queen and US king. Fitted sheets are the tripwire: a sheet made for a 200 cm mattress will bag on a 190 cm one, and a sheet for a 137 cm width will strain over a 135 cm mattress of greater depth. Measure width, length and depth, and buy bedding for the mattress you own, not the name it shares with another country's size.
Before ordering across the Atlantic
Check four things in this order: the mattress dimensions against your frame's internal measurements (frames are built for their own country's sizes), the room's doorways and stair turns for delivery (a super king or US king will not bend around a tight landing), the bedding sizes you already own, and the return policy — a mattress is one of the few purchases where a 2 cm error cannot be fudged. If you are moving countries, budget for new bedding with the new mattress; it is cheaper than discovering the mismatch after the delivery van leaves.
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