Chocolate Plain Cotton fitted sheet stretched over a mattress, with the elastic corner in view

Deep and Extra Deep Fitted Sheets: What Depth Do You Need?

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Short answer. There is no UK standard for "deep" or "extra deep", so ignore the label and compare centimetres. Measure your mattress from base to top, add any topper, and buy a fitted sheet whose depth is the same or more. As a rough guide, sheets sold as deep usually fit about 30 to 35 cm and extra deep about 38 to 40 cm. Our standard fitted sheets fit mattresses up to 35 cm (about 14 inches).

Mattresses have got thicker. A traditional open-coil mattress was often around 20 cm deep, while a modern pocket-sprung or pillow-top mattress can be 30 cm or more before you add a topper. Fitted sheets have followed, which is why shops now sell standard, deep, extra deep and even "ultra deep" sheets. The trouble is that each brand draws those lines in a different place. This guide shows how to measure, what the labels tend to mean, and how to choose.

Checked against our fitted sheet range and several UK retailers' labels on 6 November 2026.

How to measure mattress depth

  1. Take the bedding off so you are measuring the mattress itself.
  2. Stand a tape measure upright against the side of the mattress, at the middle of the long edge.
  3. Measure from the bottom edge to the highest point of the top surface. On a pillow-top, that is the top of the pillow layer.
  4. If a topper stays on the bed all the time, add its thickness. As far as the sheet is concerned, the topper is part of the mattress.
  5. Do not measure the bed frame or the divan base. Only the part the sheet wraps around counts.
A fitted sheet on a mattress, showing the depth of its elasticated skirt
Measure the mattress vertically, base to top surface, with the topper included.

Deep vs extra deep: what the labels usually mean

These are typical ranges from UK shops, not fixed definitions. One brand's "extra deep" can be another brand's "deep", so treat the table as a starting point and check the figure on the pack.

Label you will see Typical sheet depth Typical mattress
Standard about 25 to 30 cm Open coil and thinner foam mattresses
Deep about 30 to 35 cm Most pocket-sprung and hybrid mattresses
Extra deep about 38 to 40 cm Pillow-tops, or a deep mattress with a topper
Ultra or extra extra deep about 45 cm and over Very deep mattresses with a thick topper

Because the labels overlap, two sheets both called "deep" can differ by 10 cm. The only reliable comparison is your measurement against the sheet's stated depth.

How deep are our fitted sheets?

Every fitted sheet we sell is cut for mattresses up to 35 cm deep, about 14 inches. That puts our standard sheet in the range most shops call deep, and it covers most UK mattresses, including many pillow-tops. It is the same depth in all three sheet fabrics and every size:

For mattresses from 15 to 20 inches (about 38 to 51 cm), we tailor a deeper skirt, which you can choose as the mattress height when you build your set. For anything deeper, or for a non-UK mattress size, send the measurements through our custom sizes form.

Charcoal French linen fitted sheet with matching pillowcases on a pale oak bed
All four fabrics are cut to the same 35 cm depth.

Signs your fitted sheet is too shallow

  • A corner pops off during the night, usually the one nearest where you sleep.
  • The elastic does not reach under the mattress and sits on the side instead.
  • The sheet feels drum-tight across the top and pulls into ridges.
  • The seams wear through at the corners after a few months.

None of these can be fixed with sheet straps for long. The answer is a deeper sheet. If you have recently added a topper, that is very often the cause.

What if the sheet is too deep?

A sheet a few centimetres deeper than the mattress is fine: the extra fabric tucks underneath and the elastic holds it. That is why, if you are between two depths, the deeper one is the safer buy. A sheet that is very much too deep, say 40 cm on a 20 cm mattress, will leave loose fabric on the sides that wrinkles. For thin mattresses, a standard-depth sheet looks neater.

Choosing a depth: three examples

  • A 25 cm pocket-sprung mattress, no topper. Any sheet labelled 30 cm or more fits, including ours at 35 cm.
  • A 28 cm mattress with a 5 cm topper. That is 33 cm in total. A 35 cm sheet fits; a 30 cm sheet will struggle.
  • A 32 cm pillow-top with a 7 cm topper. That is 39 cm. You need an extra deep sheet, or our deeper tailored skirt.

For the width and length of each fitted sheet, see bed sheet sizes UK. If you are choosing a fabric at the same time, our percale vs sateen comparison and linen vs cotton guide may help.

Deep fitted sheet questions

What is the difference between deep and extra deep fitted sheets?

There is no fixed UK definition. Sheets sold as deep usually fit mattresses of about 30 to 35 cm, and extra deep about 38 to 40 cm, but brands vary, so compare the depth in centimetres.

How deep is a standard fitted sheet in the UK?

Many UK shops sell standard fitted sheets for mattresses of about 25 to 30 cm. Our standard fitted sheets are cut deeper, for mattresses up to 35 cm.

Do I need a deep fitted sheet with a mattress topper?

Often, yes. Add the topper's thickness to the mattress depth and buy a sheet at least that deep. A 5 cm topper on a 28 cm mattress needs a sheet for 33 cm or more.

How do I measure my mattress for a fitted sheet?

Stand a tape measure upright against the side of the mattress and measure from the bottom edge to the top surface, including any topper. Do not include the bed frame or base.

Can I use an extra deep fitted sheet on a normal mattress?

Yes, if it is only a little deeper. The extra fabric tucks under the mattress. On a thin mattress a very deep sheet leaves loose fabric on the sides.

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