A fitted sheet only fits properly when you know not just the length and width, but also the depth of your mattress. That third measurement is often forgotten. So always measure your mattress itself, without any bedding around it. The external dimensions of your bed or bed frame tell you nothing about the right fit.
With a standard mattress, you need not only the mattress depth but also extra room to tuck the fitted sheet neatly under the corners. With a topper or split topper, it works slightly differently: you either measure only the topper, or the total depth of everything going under the same fitted sheet. Then compare your measurement with the stated pocket depth or maximum mattress depth on the product page. That helps you avoid corners coming loose, creases and the sheet shifting in bed.
Why your fitted sheet comes loose or pulls tight
If a fitted sheet does not sit properly, it is far from always the length or width. Often, the depth is what is wrong. After all, a fitted sheet has to go over your mattress, drop around the corners and stay tucked under the edges. If it is too shallow, the corners spring off, the elastic comes under tension and seams pull crooked. If it is too roomy, you get creases and the fabric is more likely to shift while you sleep. If this keeps happening, read fitted sheet keeps coming off — how to fix it for practical sizing and fit tips.
The right fit feels more settled, looks neater and saves hassle when making the bed. A well-fitting fitted sheet stays in place better and lies smoother under your body. It simply feels better to sleep on.
How to measure your mattress and fitted sheet depth in 3 steps
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Take all the bedding off your bed first. Always measure the mattress itself, not the bed frame and not the external size of the bed either. A bed surround can look larger, while the mattress is smaller or deeper than you think.
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Measure the length and width as precisely as possible. Note the size in centimetres and, if needed, compare it with the bedding sizing guide, including if you have an extra-long mattress of 210 or 220 cm. If you have two separate mattresses next to each other, measure them separately before deciding whether one large fitted sheet is practical.
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Then measure the depth straight up. That is the basis for measuring mattress depth for a fitted sheet. Only include what will actually go under the same fitted sheet. If you use a fitted sheet only over the mattress, measure only the mattress. If you put one fitted sheet over the mattress and topper, or over the mattress and a thicker protector, measure the total depth of both together.
What fitted sheet depth do you need?
The pocket depth is the depth of the fitted sheet corner. It needs to be deep enough to go over the edge of your mattress and still grip underneath the mattress. As a practical rule of thumb, you can work from your measured depth plus about 5 to 10 cm of tucking allowance. If you see a maximum mattress depth on a product page, compare that directly with your measured total depth.
| Measured depth | Practical guideline | How to read the product specification |
|---|---|---|
| 15 cm | Often look for a pocket depth of about 20 to 25 cm | If it says "suitable up to 15 cm", compare that directly; if it only states pocket depth, that also needs to include tucking allowance |
| 20 cm | You will often end up at about 25 to 30 cm pocket depth | This is a very common situation with standard mattresses |
| 25 cm | Often look for around 30 to 35 cm pocket depth | A deeper mattress needs more fabric to stay snug under the corners |
| 25 cm with rounded edge or extra-thick protector | Better to allow a bit of extra margin | Rounded and deeper mattresses "use" more depth than a neat, low-profile mattress |
Topper, split topper or mattress protector? Then you measure slightly differently
- Topper on its own? Then measure the topper itself. If you use a separate topper fitted sheet, only that depth is relevant.
- One fitted sheet over mattress and topper? Then measure the total depth of both together. Otherwise you will often be just short of fabric in the corners.
- Split topper? Look at more than just the length and width, but also the depth and whether the split suits your adjustable setup.
- Molton or thick mattress protector? That adds bulk. Especially with slightly deeper mattresses, it can make the difference between a snug fit and corners that keep springing loose.
- At SJUMO you will find regular fitted sheets, topper fitted sheets in Organic Cotton and split topper fitted sheets in Organic Cotton, Tencel Sateen and silky smooth. Always check the size and depth specification for each product.
Common sizes: from 90x200 to 180x200
Most measurements translate into a standard size. If you have a 180x200 bed and you are still unsure Which bedding size do I need?, what matters most is whether you have one large mattress or two separate mattresses.
| Situation | Popular fitted sheet size | Practical advice |
|---|---|---|
| 1 mattress of 90x200 | 90x200 | Then check the right pocket depth |
| 1 mattress of 140x200 | 140x200 | Also measure whether your bed is extra long |
| 1 mattress of 160x200 | 160x200 | Makes sense if you have one continuous mattress |
| 1 mattress of 180x200 | 180x200 | Usually fits best if it really is one large mattress |
| 2 separate mattresses of 90x200 on a 180x200 bed | Often 2x 90x200 | More practical for adjustable beds; with a shared topper, a topper or split topper solution is often more practical |
| Extra-long mattress | 90, 140, 160 or 180 x 210/220 | Always take the length exactly from your measurement |
Before you order: check these points
- Look beyond just the size. The product specification for pocket depth or maximum mattress depth determines whether a fitted sheet really fits well.
- Allow for stretch. Not every fitted sheet is equally forgiving. A style with less stretch needs more accurate measuring, while a more flexible fabric can sometimes give you a little more leeway.
- Do not automatically choose a bigger size. Slight shrinkage after washing can play a part, but a fitted sheet that is too roomy causes creases and shifting more quickly than a size measured properly.
- Do not assume one fixed maximum depth for every brand or shop. It varies by model. So the product specification of sustainable fitted sheets is always the deciding factor.
