Fitted sheet dimensions: pocket depth, mattress, the right measurement

A fitted sheet that comes off at night is almost never too narrow. It is too shallow. That depth has a name — the pocket — and it is the least-read measurement on product pages. It is also the leading cause of returns for this piece.

What exactly is the pocket depth?

A fitted sheet has three dimensions, not two. Width and length, which match the mattress. And the pocket: the height of the elasticated flap that goes down the side of the mattress and tucks underneath.

A 160x200 fitted sheet with a 25 cm pocket on a 30 cm deep mattress only grips the last 25 centimetres. The elastic is under constant tension, the corners ride up, and after three nights you have to remake the bed. The fabric is not to blame.

The rule: pocket depth = mattress depth + 3 to 5 cm. These few centimetres of margin let the elastic go under the mattress and hold without pulling on the seam.

Measuring your mattress: three numbers, five minutes

Width and length. Bare mattress, with a tape measure, from edge to edge. Do not measure the bed frame: it is always wider than the mattress. A mattress sold as 140 is often 139 or 141 in reality, which does not matter at all.

Depth. In the middle of a long side, not in a corner where the mattress is compressed. This is the number that decides the pocket depth.

What stays on permanently. Topper, mattress protector, underpad: anything that does not move adds to the depth.

Length deserves special attention. Two 140 cm mattresses can be 190 or 200 cm long. Those 10 cm are the difference between a sheet that stays on and one that pops off. The details are covered in the bed linen size guide.

Which pocket depth for which mattress depth

Mattress depth	Pocket depth to aim for	Type of mattress
up to 18 cm	25 cm	Foam, child's bed, sofa bed
18 to 24 cm	25 to 30 cm	Most sprung or latex mattresses
24 to 30 cm	30 to 35 cm	Deep pocket springs, memory foam
over 30 cm	35 to 40 cm	Mattress with topper, box spring

Between two pocket depths, take the deeper one. It is the only bed linen dimension where rounding up costs nothing: the extra goes under the mattress and cannot be seen.

A topper changes the calculation

A topper adds 4 to 8 cm. A quilted mattress protector, 1 to 2 cm. A 24 cm mattress with both becomes 30 or 34 cm in reality, and the fitted sheet bought for 24 cm no longer stays on.

There are two ways to handle it. Either the fitted sheet covers everything, and you need a 35 to 40 cm pocket. Or you put the mattress protector directly on the mattress and the fitted sheet over the topper: each layer holds on its own and is washed separately. The quilted waterproof mattress protector, available from 90x190 to 180x200, stays in place thanks to a deep elasticated skirt all the way round.

Too big, it creases

The opposite mistake also exists. A fitted sheet whose pocket is much deeper than the mattress will not pull taut: the excess fabric rides up on top and forms creases under your back. You can feel them, especially on a firm mattress.

The same goes for width. A 150x200 on a 140x200 mattress floats, and the elastic does not have enough mattress to grip to stay in place. Unlike a duvet cover, where a few extra centimetres read as drape, a fitted sheet is chosen in the exact size.

The elastic matters as much as the size. There are two finishes. Elastic only at the four corners holds well on a thin mattress, but leaves the long sides free: the sheet rides up in the middle. Elastic all the way round spreads the tension and keeps the sheet taut over the whole surface, even when two people move.

On a deep mattress, it is this detail — more than the fabric — that decides whether the bed will still be made when you wake up.

Noctua fitted sheets, size by size

Model	Sizes	Fabric and feel
400 thread count Egyptian cotton fitted sheet	140x190 · 140x200 · 160x200 · 180x200	100% long-staple Egyptian cotton, smooth, almost satiny feel, washable at 40 °C
Soft cotton fitted sheet	140x190 · 140x200 · 160x200 · 180x200	100% cotton, breathable, for everyday use
Washed linen fitted sheet	140x190 · 140x200 · 160x200 · 180x200	100% washed linen, cool in summer, washable at 30 °C, no ironing

All three models come in 140 in both lengths, 190 and 200 cm, and all have elastic all the way round — the finish that holds on a deep mattress. The 400 thread count Egyptian cotton fitted sheet for a smooth feel, the soft cotton fitted sheet for everyday use, the washed linen fitted sheet for sleepers who run hot. All three are gathered in fitted sheets, and the rest of the set in bed linen.

Get the tape measure out before ordering. Five minutes now are better than a return parcel next week.