Bedding Size & Fit Calculator
Match your mattress size and depth to the fitted-sheet pocket and duvet-cover size you need, so new bedding fits the first time.
Depth is the spec everyone forgets
People buy sheets by size name and are surprised when they won’t stay on. The size name only sets width and length; the number that actually decides whether a fitted sheet grips is the mattress depth, and today’s mattresses are much taller than they used to be. Get the pocket depth right and the corners stay put; get the size standard right and the duvet cover fits the duvet.
Not sure of your exact size? Start with the Mattress Size Guide, then match a duvet to your room with the Duvet Tog Calculator.
Frequently Asked Questions
Why do my fitted sheets keep popping off?
Almost always because the sheet's pocket is too shallow for the mattress. A fitted sheet grips by wrapping under the mattress, so it needs a pocket deeper than the mattress itself — usually about 5 cm more, to tuck under. Modern pillow-top and hybrid mattresses are far deeper than the sheets bundled with cheap sets, so the corners can't reach underneath and ping off. Measure your mattress depth and buy a pocket that clears it.
What do standard, deep, and extra-deep pockets mean?
They're the three fitted-sheet depth categories. Standard pockets suit mattresses up to about 30 cm deep, deep pockets cover roughly 30–40 cm, and extra-deep pockets handle 40 cm and beyond — the tall pillow-top and boxed hybrid mattresses. This calculator takes your mattress depth, adds a tuck allowance, and tells you which category to buy.
How do I choose a duvet-cover size?
A duvet cover matches the duvet, and the duvet matches (or slightly overhangs) the mattress. So the cover size follows your bed size — a Queen bed takes a Full/Queen duvet and cover, a UK Double takes a Double duvet, and so on. For a very deep mattress, some people size the duvet up one so it drapes far enough down the sides. The calculator shows the duvet size and dimensions for your mattress size.
Do US and UK bedding sizes match?
No. US and UK mattress and bedding sizes are set to different standards and don't interchange — a US Queen duvet won't fit a UK King bed, for example. Always buy sheets, covers, and duvets in the same standard as your mattress. Pick the right standard at the top of the calculator so the sizes it returns match what you'll find in the shops.
Sizing guidance based on standard bedding conventions. Measure your own mattress and confirm product dimensions before buying. Not professional advice.