Short answer: the six standard US sizes are twin at 38 by 75 inches, twin XL at 38 by 80, full at 54 by 75, queen at 60 by 80, king at 76 by 80 and California king at 72 by 84. Queen is the most common in US homes, and king and California king differ by four inches in each direction rather than in area.
The size you can buy is decided by the room as much as by the bed, so the second table here is the one most people need.
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The standard sizes
| Size | Inches | Centimeters | Width per person | Suits |
|---|---|---|---|---|
| Crib | 28 x 52 | 71 x 132 | — | Infants and toddlers |
| Twin | 38 x 75 | 97 x 191 | 38 in | Children, single adults under 6 ft |
| Twin XL | 38 x 80 | 97 x 203 | 38 in | Taller single adults, dorms, half of a split king |
| Full (double) | 54 x 75 | 137 x 191 | 27 in for two | One adult with room, or two at a squeeze |
| Queen | 60 x 80 | 152 x 203 | 30 in for two | Two adults. The default US size |
| King (Eastern) | 76 x 80 | 193 x 203 | 38 in for two | Two adults with space, or with a child or pet |
| California king | 72 x 84 | 183 x 213 | 36 in for two | Taller sleepers who will trade width for length |
A king gives each person exactly the width of a twin bed. That is the easiest way to picture it, and it is why a king suits couples who move around at night.
The room each size needs
The rule of thumb is 24 to 30 inches of walking space on any side you need to get past, and at least 36 inches in front of a wardrobe or a dresser with drawers that open.
| Size | Minimum room | Comfortable room |
|---|---|---|
| Twin | 7 x 10 ft | 8 x 10 ft |
| Twin XL | 7 x 10 ft | 8 x 10 ft |
| Full | 9 x 10 ft | 10 x 12 ft |
| Queen | 10 x 10 ft | 10 x 14 ft |
| King | 12 x 12 ft | 13 x 15 ft |
| California king | 12 x 12 ft | 12 x 16 ft |
Two adjustments. A bed against a wall needs clearance on three sides rather than four, which gains you a size in a tight room. And a bed frame is wider than the mattress: allow 2 to 5 inches on each side for the frame, and more for an upholstered one.
Check the route before you order
- Doorways. A queen mattress is 60 inches wide and a standard interior door is 30 to 32. Mattresses turn on their side, but a rigid box spring does not bend at all, which is the reason split box springs exist.
- Stair turns. Measure the diagonal at the tightest landing. This is where king mattresses stop.
- Ceiling height at the stairs. Standing a mattress on end needs headroom you may not have.
- Whether it arrives boxed. A compressed mattress in a carton solves all three problems, which is one of the reasons the format took over. What it does and does not include is in the mattress in a box guide.
Split sizes, for adjustable bases
| Name | Made of | Total | Notes |
|---|---|---|---|
| Split king | Two twin XL, 38 x 80 each | 76 x 80 | Same footprint as a king. Each side moves independently |
| Split California king | Two halves of 36 x 84 | 72 x 84 | Not made of twin XL, so far fewer models fit it |
| Flex top king | One king mattress, split head section only | 76 x 80 | No seam under your body, and less independence |
These only make sense on an articulating base, and the trade offs are in split king vs king and what is a split king. The bedding changes too, which catches people out, as we cover in sheets for adjustable beds.
Choosing between two sizes
- Full or queen? Queen unless the room forces it. A full gives two adults 27 inches each, which is narrower than a crib is long. The comparison is in full vs queen.
- Queen or king? King if you have the room and either of you moves at night. The cost difference runs through the frame and the bedding too, which is in king vs queen.
- King or California king? California king only if someone is over about 6 ft 2, because you trade four inches of width for four inches of length.
- Twin or twin XL? Twin XL for anyone over about 5 ft 10, and for any bed that might later become half of a split king.
Height matters as much as footprint
The size chart says nothing about how high the bed ends up, and that is what people notice daily. Add frame height, any foundation and mattress thickness: most adults are comfortable with the sleep surface between 24 and 26 inches, roughly knee height. The arithmetic is in platform bed vs box spring, and whether you need a foundation at all is in do you need a box spring.
Common questions
What is the most common mattress size? Queen, at 60 by 80 inches. It fits two adults and fits a 10 by 10 foot room, which is the combination that made it standard.
Is a king or California king bigger? Neither by much. A king is wider at 76 inches, a California king is longer at 84. The king has slightly more surface area.
What is the difference between a full and a double? Nothing. They are two names for the same 54 by 75 inch size, sold as full in the US and double elsewhere. Note the length: a full is 75 inches, five shorter than a queen.
What size mattress do two adults need? Queen at minimum. A full gives each person 27 inches, which is less than a twin bed and is the size most couples upgrade away from.
Do European mattress sizes match US ones? No. European sizes are metric and none of them lines up with a US size, so an imported frame usually needs an imported mattress and imported bedding.
The bottom line
Take the size from the second table rather than the first. Measure the room, subtract 24 to 30 inches of walking space on every side you use, and check the stair turn before ordering anything that does not arrive compressed. Then check the height, because a bed that fits the room can still be the wrong height to get out of.
