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 retail sizes, confirmed against the source linked below. Individual mattresses vary by up to an inch between manufacturers, and a bed frame adds roughly 2 to 5 inches to each dimension — measure the frame, not the mattress, when the room is close. Minimum room is the mattress plus 24 in of clear floor on each side and at the foot; comfortable is the same at 36 in.
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 reports four states, using the same clearances the chart above is built from. Comfortable is 36 inches or more of clear floor on the tightest side — nightstands fit and two people can pass. Workable is 24 to 35 inches: this is the chart's minimum room, and it is genuinely liveable, but it is the minimum. Tight is 15 to 23 inches: enough to walk, not enough for a nightstand on both sides. Does not fit is anything under 15 inches. Clearance is measured as the narrowest of the two sides and the foot, and the mattress is tried in both orientations with the better one kept.
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.
Fitting the room and suiting the sleepers are two different questions, and the calculator answers them separately. A Twin fits almost any room comfortably; that does not make it the right bed for two adults. Where the two lists disagree, the room is the constraint, not the mattress.
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 Twin or Twin XL fits comfortably, with 40 inches or more of clear floor. A Full, Queen or California King is workable — a Queen leaves 30 inches on the tightest side, which clears the 24-inch minimum but is under the 36 inches that counts as comfortable. A standard King is tight: at 76 inches wide it leaves 22 inches per side, walkable but with no room for a nightstand on both sides.
Yes, comfortably. A Queen is 5 ft by 6 ft 8 in, and laid across the 12 ft dimension it leaves about 40 inches of clear floor on the tightest side — above the 36-inch comfortable threshold, not merely above the 24-inch minimum.
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.