What size is a king bed sheet?
A standard US king sheet set fits a mattress 76 inches wide and 80 inches long. You need a flat sheet about 108 by 102 inches and a fitted sheet with 16-inch-deep pockets for most modern mattresses. This guide gives you the exact numbers, explains California king sizing, and shows how to check pocket depth so the sheet stays put.
What are the standard king flat sheet dimensions?
A standard king flat sheet measures 108 inches wide by 102 inches long. The sheet is cut larger than the mattress to allow for tucking. A king mattress is 76 inches wide by 80 inches long, so the extra 32 inches of width and 22 inches of length give you enough fabric to tuck the sheet under the mattress on both sides and at the foot of the bed.
Different brands cut their flat sheets slightly differently. Some run 106 to 110 inches wide, and the length can vary from 100 to 104 inches. A deeper mattress uses more of that width when you tuck the sheet in. If your mattress is taller than 14 inches, a flat sheet on the shorter end of the range may not leave enough fabric to fold over the top edge of a blanket.
Flat sheets have no elastic corners, so the generous width also gives you room to move in your sleep without pulling the sheet loose from one side. When you shop, check the listed dimensions rather than relying on the word "king" alone. The bed linen sizes and fit guide on our blog walks through what to watch for across all standard mattress sizes.
What size is a king fitted sheet?
A standard king fitted sheet measures 78 inches wide by 80 inches long. These dimensions match the top surface of a king mattress, so the sheet fits snugly without shifting. The length and width are consistent across most brands, because mattress makers follow the same sizing convention.
The pocket depth determines whether the sheet stays put. Most king fitted sheets come with a pocket depth of 14 to 16 inches. If your mattress is thicker than 14 inches, or you use a mattress topper, look for a deep pocket sheet with a depth of 17 inches or more. A sheet with a pocket that is too shallow pulls loose at the corners every night.
Always check the pocket depth on the packaging before you buy. A fitted sheet that matches the surface dimensions but has the wrong pocket depth simply won't work. For a mattress over 16 inches thick, you may need a sheet labeled extra deep pocket, which accommodates up to 20 inches.
How do I measure my mattress for a king fitted sheet?
A standard king mattress is 76 inches wide by 80 inches long, so the length and width are rarely the issue. The measurement that matters most for a fitted sheet is the depth. A pocket that is too shallow pulls the corners up at night.
- Clear the mattress of all bedding, including any mattress protector.
- Place a tape measure against the floor or the box spring and measure straight up to the top edge of the mattress.
- If you use a foam topper, leave it on and measure from the floor to the top of the topper. The fitted sheet has to wrap around the whole stack.
- Measure at two points: the side rail and the foot of the bed. Mattresses can settle unevenly.
- Round up to the nearest half inch. A 13.5-inch mattress calls for a 14-inch pocket, not a 13-inch one.
Once you have your number, look for a fitted sheet with a pocket depth at least one inch greater than your measurement. For a mattress and topper combination that measures 15 inches, a 16-inch pocket gives the elastic room to pull under the corner without sliding off. A deep pocket sheet with an all-around elastic band holds more securely on thicker setups than one with elastic only at the corners.
King vs. California king sheet size: what is the difference?
A standard king fitted sheet does not stay on a California king mattress. The two sizes look similar at a glance, but the width and length are swapped. A king mattress measures 76 inches wide by 80 inches long. A California king is narrower and longer at 72 inches wide by 84 inches long. The extra four inches of length on a California king mean the fitted sheet pockets are positioned differently, and the flat sheet is cut to match.
If you try to stretch a king fitted sheet onto a California king mattress, the corners pull loose overnight because the pocket spacing does not line up. The flat sheet also falls short on the sides of a king when sized for a California king. Before buying, check the label for the exact width and length rather than relying on the word "king" alone.
| King | California king | |
|---|---|---|
| Mattress width | 76 inches | 72 inches |
| Mattress length | 80 inches | 84 inches |
| Fitted sheet fits | 76 × 80 in | 72 × 84 in |
| Flat sheet (typical) | 108 × 102 in | 108 × 102 in |
Some brands sell the same flat sheet for both sizes because the width and length are generous enough to cover either mattress. The fitted sheet, however, is never interchangeable. If your bedroom is longer than it is wide, a California king gives you more legroom without taking up extra wall space. Measure your mattress before ordering, and match the fitted sheet dimensions exactly.
What pillowcase size comes with king sheets?
A king sheet set includes two king-size pillowcases, each measuring 20 by 36 inches (51 by 91 cm). The envelope or side opening runs along the shorter 20-inch end. That extra length compared to a standard pillowcase keeps the pillow from poking out of the fabric once it settles into a king pillowcase protector or a down fill.
Standard pillowcases are 20 by 26 inches, so a king case adds a full 10 inches of length. If you sleep on two stacked pillows or a body pillow, the longer envelope covers the whole stack without pulling tight at the seam. Some brands label this size as a “king pillow sham” when it has a flange border, but a sham is a decorative cover with a back overlap, not a sleeping case.
- A true king pillowcase is 20 by 36 inches and has a side or end opening.
- Standard cases (20 by 26 inches) do not fit king pillows and will leave an exposed edge.
- Most king sheet sets bundle two king cases; check the label before buying a set labeled simply “king,” as a few brands still pack standard cases with the flat and fitted sheets.
- If your mattress is a split king, you may receive two twin XL fitted sheets and two king cases, not four.
How to pick a sheet set that actually fits
A king sheet set is worth buying only if it stays put through the night. Three details make the difference between a crisp morning bed and a tangled mess: the pocket depth, the elastic, and how the fabric behaves after washing.
Before you order, check the label or the product specs for these points. A set that matches your mattress on paper can still slip if one detail is off.
- Measure your mattress height and add the topper depth, then pick a pocket depth at least 2 inches deeper. A 14-inch pocket on a 14-inch mattress leaves no room for tucking.
- Look for elastic that runs all the way around the fitted sheet, not just at the corners. Full-perimeter elastic grips the mattress evenly and stops the corners from popping off.
- Check whether the listed dimensions are cut size or finished size. A flat sheet listed as 108 by 102 inches may shrink to 104 by 98 after the first wash.
- Cotton and linen can shrink 3-5 % in a hot dryer. If the flat sheet barely overhangs on day one, it will be too short after a month of washing.
- Open the pillowcase description. Standard king pillowcases measure 20 by 40 inches; a “king” set that includes 20-by-36 cases is really a queen pillowcase bundled in.
- Read the return policy for opened bedding. A set that fits the stated dimensions but still does not work on your mattress should be returnable without a restocking fee.
When a brand publishes exact finished dimensions, a clear pocket depth, and the elastic style, you can buy with confidence. The same checks are explained in more detail in our guide to bed linen sizes and fit.
Frequently asked questions
Will king sheets fit a California king mattress?
No. A California king mattress is 72 by 84 inches, so it is narrower and longer than a standard king. King sheets will be too wide and too short. You need sheets labeled California king.
What does deep pocket mean for king sheets?
Deep pocket fitted sheets have side walls of 15 inches or more, designed for mattresses thicker than 12 inches. If your mattress plus a topper measures 14 inches or more, deep pocket sheets will keep the corners from popping off.
How much do king sheets shrink after washing?
Cotton sheets typically shrink 2 to 4 percent on the first wash. A 108-inch flat sheet might lose about 2 to 4 inches in length. Pre-washed or preshrunk labels mean most of that shrinkage has already happened before you buy.
Can I use king sheets on a split king mattress?
A split king is two twin XL mattresses pushed together. A single king fitted sheet will not work because each side moves independently. You need two twin XL fitted sheets and one king flat sheet with king pillowcases.