King size mattresses

What size is a king size mattress?

A UK king size mattress is 150 cm wide and 200 cm long, or 5ft x 6ft6. That's 15 cm wider and 10 cm longer than a standard double mattress, and 30 cm narrower than a super king.

The extra 10 cm of length matters if you're tall. A mattress should be about 10 to 15 cm longer than the person on it, so a 200 cm king suits people up to about 185 to 190 cm, where a 190 cm double suits people up to about 175 to 180 cm.

Is a UK king the same as an American or European king?

A UK king is smaller than both an American king (about 193 x 203 cm) and a European king (160 x 200 cm). The American king is wider than even a UK super king, while the European king, 5ft3 x 6ft6, is 10 cm wider than a UK king and the same length.

That matters if your frame came from a European brand or your bedding from an American one. A 160 x 200 cm mattress won't go into a UK king frame, and a UK king leaves a 10 cm gap down the side of a European one. Whatever a bed is called, check its centimetres before you buy a mattress for it. See European size mattresses for how the 200 cm long European sizes compare.

King or super king: which should I choose?

Choose a king if you want more room than a double without filling the bedroom, and a super king if you'd like 90 cm each, the width of a single bed. Both are 200 cm long, so the difference is 30 cm of width.

The room often decides it. Leave around 60 to 70 cm to walk past each side of the bed and the foot. With walkways on both sides, a king needs a room about 270 to 290 cm wide, plus whatever the frame adds; a super king needs about 300 to 320 cm. If you're both light sleepers, a child climbs in most nights, or one of you is much heavier, the extra width of a super king mattress is worth having.

How deep should a king size mattress be?

A standard king size mattress is about 18 to 25 cm deep, which suits an ordinary frame or divan, while deep mattresses of 25 cm and over often suit heavier sleepers who need firmer support and firm edges.

Pocket sprung king size mattresses let air move and give each of you independent support. Memory foam king size mattresses pass on very little movement, which helps if you go to bed at different times. For a heavier sleeper, see mattresses for heavier people. If a mattress lists a spring count, check which size it's quoted for, as counts are often given for a double or king, and more springs isn't automatically better. Whatever the depth, fitted sheets need a pocket deeper than the mattress.

Will a king size mattress fit up my stairs?

A rolled king size mattress is the easier choice for tight stairs, because it arrives compressed and vacuum packed in a box. A king delivered flat is 150 x 200 cm, so measure the narrowest turn on your stairs and landing first. Unbox a rolled king soon after it arrives: you can sleep on it after a few hours, and it reaches full shape within 24 to 72 hours.

Each king size mattress page shows whether it arrives rolled or flat, and its delivery time. Most of our mattresses can be delivered the next working day; the delivery page has the details.

As a family business, we'll help you weigh up a king against a super king: send us your room measurements and we'll go through the options with you.

Written by the Mattress Town team. Last updated 9 October 2026.