Size
Twin
38 × 75 in
Retailers in the United States commonly list a twin mattress at 38 by 75 inches, and some list 39 inches wide. No federal rule fixes the number. What is federally regulated about a mattress is how it behaves in a fire, not how big it is, which is a large part of why sheet fit is as inconsistent as it is.
Depths stated for Twin in this catalog
2 of the 5 items in the catalog cut for Twin state a depth on their listing. The figures below are what the sellers wrote, not what was measured here, and they are grouped by what part of the stack each item grips.
| Item | Layer | What the listing states | Deepest figure given |
|---|---|---|---|
| Amazon Basics Microfiber Sheet Set, Twin | Sheet & Pillowcase Sets | 14 in | 14 in |
| Utopia Bedding Waterproof Protector, Twin | Mattress Protectors | fits up to 15 in | 15 in |
What Twin gets confused with
Twin XL
The width is the same and the length is not. A twin sheet on a Twin XL mattress is five inches short, which shows up as a fitted sheet that will not reach the bottom corners no matter how deep the pocket is. Pocket depth cannot fix a length problem.
Single
Single is an older word for the same bed and is still used in listings and by older furniture. It is not a separate size, but it is worth reading the dimensions when you see it, because imported goods sometimes carry a different measurement under the same word.
Everything here cut for Twin
- Amazon Basics Microfiber Sheet Set, Twinin Sheet & Pillowcase Sets
- Utopia Bedding Waterproof Protector, Twinin Mattress Protectors
- EGO 3 Inch Gel Memory Foam Topper, Twinin Mattress Toppers
- SINWEEK 2 Inch Gel Memory Foam Topper, Twinin Mattress Toppers
- EGOHOME 2 Inch Gel Memory Foam Topper, Twinin Mattress Toppers
To add your own layers up and see what pocket depth the result needs, use Pocket Check. To see the other four sizes side by side, go to Sizes.
Where this comes from
What is federally regulated about a mattress is how it behaves in a fire, not how big it is. These are the rules that do exist.