King Size Mattresses in Memory Foam and Pocket Sprung
The king is the size to move up to when a double stops being enough, and it changes two things at once. It is 6in (15cm) wider than a double at 5ft (150cm), and it is the first UK size that gets longer: 6ft 6in (200cm) against 6ft 3in. For anyone over about 6ft 2in, that extra length matters more than the width.
Every mattress here is 5ft x 6ft 6in (150 x 200cm) and fits any UK king frame. Worth checking if your bed came from abroad, though: an American king is far larger at roughly 193 x 203cm, closer to a UK super king than to this.
Memory foam king size mattresses
Foam forms to the sleeper and spreads their weight rather than resisting it at the hips and shoulders.
What it does best on a king is isolate movement. Foam transmits very little across the surface, so a partner turning over, getting up early or coming to bed late barely registers on the other side. On a bed this wide the two sleepers are far enough apart that foam removes the disturbance almost entirely.
Foam holds warmth, and a larger surface with two people on it holds more. The versions made with gel through the layer sleep noticeably cooler.
Pocket sprung king size mattresses
Each spring sits in its own fabric pocket and compresses independently of the ones beside it.
That matters most where two people of different weights share a bed. The springs under each sleeper respond to that sleeper alone, so the heavier one does not set the shape of the mattress for both, and neither person rolls towards the middle the way they would on an older open-coil mattress.
Air moves between the pockets, so these run cooler than foam, and the surface feels springier rather than sinking. A pillow top, where a mattress has one, is a padded layer stitched over the springs that softens the feel without changing the support underneath.
Firm king size mattresses
Firm holds the body higher and lets it sink in less; softer lets the shoulders and hips settle further before taking the weight. Back and front sleepers and heavier sleepers generally want firmer, side sleepers less.
On a king the complication is that two people are choosing one mattress. Where preferences differ, medium-firm with a comfort layer over it suits both better than either extreme, since the surface can be softened later on one side with a topper while the support stays constant.
That is also the part worth doing in person. Whether two people settle on the same mattress, and whether one of you notices the other moving, is not something a specification answers. Our Enniskillen showroom has mattresses out on the floor, and the useful test is both of you lying on one at the same time, not one at a time.
King size mattress FAQs
What size is a king size mattress?
5ft x 6ft 6in, or 150 x 200cm, in the UK and Ireland.
How long is a king size mattress?
6ft 6in (200cm), which is 3in longer than a single, small double or double.
What is the difference between a king and a super king?
Width only. A super king is 6ft (180cm) against the king's 5ft (150cm). Both are 200cm long.
Is a UK king the same as an American king?
No. An American king is roughly 193 x 203cm, much wider than a UK king and closer to a UK super king. Neither the mattress nor the bedding is interchangeable.
Will a king size mattress fit up my stairs?
At 150cm it is wider than a double and does not turn as easily on a staircase with a half landing. Measure the narrowest turn before ordering, particularly in an older house.
What is a zip and link mattress?
Two narrow mattresses joined by a zip, making one king size surface. It lets each side be a different firmness, and it goes up stairs and round corners that a single-piece king will not.