Calculator + chartEnter your measurements below and it works the answer out.
A twin is 38 × 75 in, a full 54 × 75, a queen 60 × 80 and a king 76 × 80. Every US mattress size below with exact dimensions, and the smallest room each one fits in.
| Size | Inches | Centimeters | Minimum room | Comfortable room | Best for |
|---|---|---|---|---|---|
| Twin | 38 × 75 | 97 × 191 | 8 × 9 ft | 10 × 10 ft | Children, single sleeper, bunk beds |
| Twin XL | 38 × 80 | 97 × 203 | 8 × 9 ft | 10 × 10 ft | Taller single sleeper, dorm rooms |
| Full (Double) | 54 × 75 | 137 × 191 | 9 × 9 ft | 11 × 10 ft | One adult with room to spread, guest rooms |
| Queen | 60 × 80 | 152 × 203 | 9 × 9 ft | 11 × 10 ft | Two adults — the most common US size |
| King | 76 × 80 | 193 × 203 | 11 × 9 ft | 13 × 10 ft | Two adults wanting maximum width |
| California King | 72 × 84 | 183 × 213 | 10 × 9 ft | 12 × 10 ft | Sleepers over 6 ft — 4 in longer, 4 in narrower than King |
| Split King | 2 × (38 × 80) | 2 × (97 × 203) | 11 × 9 ft | 13 × 10 ft | Adjustable bases, partners with different firmness needs |
Dimensions are the US industry standard and are consistent across manufacturers. Actual mattresses vary by up to an inch, and bed frames add roughly 2–5 inches to each dimension.
Both room columns come from one rule, so the table and the calculator always agree.
Minimum room = the mattress plus 24 inches of walking space on each side and 24 inches at the foot, rounded up to the next whole foot. Twenty-four inches is the narrowest gap an adult can walk through without turning sideways.
Comfortable room = the same with 36 inches on each side and at the foot — enough for nightstands, a wardrobe door that opens, and someone walking past while another person gets into bed.
The calculator uses the minimum rule and reports three states: fits comfortably at 24 inches or more of clearance, fits tight between 15 and 24 inches, and does not fit below 15. It tries the mattress in both orientations and keeps whichever works better.
Neither figure accounts for wardrobes, inward-swinging doors, radiators or bay windows. If your room has any of those, measure the clear floor area rather than the full room.
Neither, quite. A standard King is 4 inches wider (76 vs 72) and a California King is 4 inches longer (84 vs 80). Their total area is almost identical — 6,080 against 6,048 square inches. Choose California King only if someone sleeping in it is over about 6 ft 2 in; otherwise the extra width of a standard King is more useful.
A Queen fits comfortably — it leaves 30 inches on each side and 40 at the foot. A California King also clears the minimum, at exactly 24 inches per side. A standard King is the one that struggles: at 76 inches wide it leaves 22 inches per side, which is walkable but tight and leaves no room for nightstands.
Yes, comfortably. A Queen is 5 ft by 6 ft 8 in, leaving roughly 2 ft 6 in on each side in a 10 ft width — above the 24-inch minimum, with space at the foot as well.
No. A Twin XL is 38 inches wide, a Full is 54. A Twin XL is a single bed made 5 inches longer; a Full is 16 inches wider and 5 inches shorter than a Queen.
Yes. Two Twin XLs side by side measure 76 by 80 inches, exactly a standard King. That is what a Split King is, and it is why adjustable bases are usually sold in that configuration.
Sheets are sold by the mattress size name, so a Queen mattress takes Queen sheets. The number that catches people out is pocket depth — measure your mattress height and buy deep-pocket sheets if it is over 14 inches.