Deep pocket sheets: how to measure your mattress first
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Measure your mattress before you buy, because "deep pocket" is not a defined term. One brand calls 13 inches deep, another starts deep at 15, and a third prints "extra deep" on a sheet that fits 16. The only number that matters is the pocket depth in inches on the listing, and the only way to use it is to know your own mattress depth first.
Run a tape measure from the seam at the top edge of the mattress straight down to the seam at the bottom edge. Add the thickness of anything you put on top of it. Buy a fitted sheet whose stated pocket depth is larger than that total.
"Deep pocket" is a marketing word, not a measurement
There is no body that defines it. Compare two retailers writing guides on the same subject and the numbers do not line up. California Design Den puts standard pockets at roughly 7 to 14 inches, deep at 15 and up, and extra-deep at 18 and up. South Shore Fine Linens puts standard at 7 to 14, deep at 13 to 17, and extra-deep anywhere from 16 to 25 inches depending on which paragraph you read. Their own guide calls the deep-pocket range "a huge range" and tells you to check the number on the package.
That is the correct advice, and it is worth saying why it is necessary. A sheet labelled deep pocket could be cut for a 13-inch mattress or a 17-inch one. Those are different products sold under the same word. If a listing uses the word and never gives you a figure in inches, you have not been told anything.
How to measure, in about thirty seconds
The measurement
1. Strip the bed. Measuring over a fitted sheet and a protector adds half an inch of nothing.
2. Stand a tape measure against the side of the mattress, at the middle of the long edge rather than at a corner. Corners on pillow-top mattresses curve and read short.
3. Measure from the top seam to the bottom seam. Do not include the box spring, the bed base or the frame. A fitted sheet goes over the mattress only.
4. Do not compress the mattress with the end of the tape. Let it rest.
5. Add the thickness of your topper, mattress pad and protector. Write the total down.
Most people skip step five and that is where the fitted sheet fails. A 12-inch mattress with a 3-inch topper is a 15-inch sleeping surface, and the sheets that fitted fine last year will now pop a corner at 4am. Our own BambooLux Natural Comfort Topper is 2 to 3 inches once it has fully expanded, so it moves you up one bracket on its own.
Width and length are the easy part
Depth is the number that varies. Width and length are conventional, so the size name does most of the work. In the US, per Casper's size chart: twin is 38 by 75 inches, twin XL is 38 by 80, queen is 60 by 80, king is 76 by 80, and California king is 72 by 84. Full is the one that moves — Casper lists it as 53 by 75, while GoodBed lists 54 by 75. An inch of width is absorbed by the elastic, so either way a full fitted sheet fits a full mattress.
So you do not need to measure width and length to buy sheets. You do need to measure depth, every time, because nothing about the size name tells you how thick your mattress is.
Too deep is a real problem too
Most advice treats pocket depth as one-directional: buy deeper and you are safe. That is mostly true and not entirely. Put a 20-inch pocket on a 10-inch mattress and the extra fabric has to go somewhere. It gathers under the mattress in loose folds, the elastic has nothing to pull against, and the sheet slides and wrinkles across the sleeping surface instead of staying taut. It will not ping off, but it will not look or feel right either.
The useful target is a pocket a couple of inches deeper than your measurement, not the deepest pocket you can find. Elastic that runs the whole way around the sheet rather than only at the four corners also matters more than raw pocket depth, because all-round elastic keeps tension on the underside of the mattress at every point instead of four.
The number on ours
Our BambooLux Cooling Sheet Set is 100% viscose derived from bamboo, with 16-inch pockets and elastic all the way around the fitted sheet. It comes in full at $89.99, queen at $99.99 and king at $104.99, and each set is one fitted sheet, one flat sheet and two pillowcases.
Sixteen inches is a figure, not a category. It means a 13-inch mattress with a 3-inch topper fits with nothing to spare, and a 14-inch mattress with a topper does not. We would rather you work that out with a tape measure now than discover it after the first wash, when the set is no longer returnable and the corner is already on the floor.
And if the listing you are reading instead of this one says "deep pocket" with no inches attached, write to the seller and ask for the figure. A seller who knows their own product will answer in one line.
Related: Sleep & Bedroom