UK bed sizes are standard, but fitted sheets have a second measurement most people forget about: depth. Get the width and length right and the depth wrong, and the sheet still will not stay on. This guide covers both, plus how to measure your own mattress if you are not sure what you have.
| Bed size | Centimetres | Inches | Feet |
|---|---|---|---|
| Single | 90 x 190cm | 35" x 75" | 3ft |
| Small Double | 120 x 190cm | 47" x 75" | 4ft |
| Double | 135 x 190cm | 53" x 75" | 4ft6 |
| King | 150 x 200cm | 59" x 79" | 5ft |
| Super King | 180 x 200cm | 71" x 79" | 6ft |
Every one of our fitted sheets is made to these measurements with a 40cm skirt, so the sheet measures considerably larger laid flat than the mattress it goes on. That is normal — the extra fabric is the depth, not a sizing error.
Depth is measured from the top surface of the mattress down to where it meets the base. It is the measurement that decides whether the sheet stays put.
A 40cm sheet fits everything in that list. It is cut to fit mattresses up to 40cm, not exactly 40cm, so on a shallower mattress the extra fabric simply gathers underneath rather than bagging at the sides. This is why buying deeper is the safer choice: too deep is invisible, too shallow pings off the corner in the night.
The mistake worth avoiding is measuring the mattress and forgetting the topper. A topper adds 5cm to 8cm, which is exactly enough to take a 30cm sheet out of range.
Two variations come up often in the UK:
If your mattress is one of these, measure before you buy rather than going by the name on the label. Bed size naming is not consistent between retailers, and the numbers are.
Not all fitted sheets are elasticated the same way, and it makes more difference than depth on a mattress that is borderline.
Corner elastic gathers only at the four corners. The sides of the sheet hang loose, so it relies entirely on those four points to hold tension. On a deep mattress it will work its way off.
Fully elasticated runs elastic 360° around the entire skirt. The tension is spread the whole way round, which is what keeps the edge gripped under the mattress rather than creeping up the side. Every sheet we make is fully elasticated, which is also why they fold more neatly — the edge pulls into a consistent curve instead of a lumpy one.
A UK double fitted sheet is 135 x 190cm, or 4ft6. That is the mattress measurement — the sheet itself measures larger flat, because the skirt depth is added on all four sides.
A UK king size fitted sheet is 150 x 200cm, or 5ft. Note that it is longer than a double as well as wider: 200cm rather than 190cm.
A UK single fitted sheet is 90 x 190cm, or 3ft. A small double is 120 x 190cm — same length, 30cm wider.
There is no legal standard, which is why the labels are inconsistent. In practice "deep" usually means 30cm and "extra deep" means 40cm, but always check the number rather than trusting the word.
Anything from 25cm upwards will fit, but 30cm or 40cm gives you room to add a topper later without buying new sheets. A 25cm sheet on a 25cm mattress has no tolerance at all.
It will go on, but it will not stay tight. A double is 15cm wider, so the excess bunches underneath and the sheet loosens as you move. A sheet cut to 120cm holds its tension properly.
Nine times out of ten it is a depth problem, not a quality problem — the sheet is too shallow for the mattress and the corners are under constant tension. Measure the mattress with the topper on and size up. Fully elasticated sheets also hold far better than corner-elastic ones.
Wishlist is empty.
