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In the US, a standard King (also called Eastern King) mattress is 76 × 80 inches (193 × 203 cm). A California King runs narrower and longer: 72 × 84 inches (183 × 213 cm). Split King keeps that same 76 × 80 footprint, but two Twin XL mattresses (38 × 80 inches each) make it up, so each side moves on its own on an adjustable base. Budget a bedroom of 12 × 12 feet or more, and measure your stairwell turns before you order. Width is what gets stuck, not thickness.
King size mattress dimensions in the US
Retailers in the US and Canada share the same size names and the same inch measurements. Manufacturing tolerance runs about ±1 inch, which is why a tight-fitting frame sometimes needs persuading. The Better Sleep Council (the consumer arm of the International Sleep Products Association) publishes size charts built on these same figures.
| Size | Inches | cm | Sq ft | Fitted sheet |
|---|---|---|---|---|
| Queen (for reference) | 60 × 80 | 152 × 203 | 33.3 | Queen |
| Twin XL | 38 × 80 | 97 × 203 | 21.1 | Twin XL |
| King / Eastern King | 76 × 80 | 193 × 203 | 42.2 | King |
| California King | 72 × 84 | 183 × 213 | 42.0 | Cal King (not interchangeable) |
| Split King | 2 × (38 × 80) | 2 × (97 × 203) | 42.2 | Two Twin XL, or a split-king set |
| Split Cal King | 2 × (36 × 84) | 2 × (91 × 213) | 42.0 | Special order |
Look at the sq ft column for the surprise. A King is fractionally larger in surface area than a Cal King, because Cal King trades 4 inches of width for 4 inches of length.
King vs California King vs Split King
King (76 × 80)
The default for couples. Each person gets 38 inches, the width of a twin bed. Sheets, frames and foundations come in the widest range here, and no other size shows up on sale as often.
California King (72 × 84)
Choose it when someone in the bed clears 6 ft 2 in, or when the room runs long and narrow. You give up 4 inches of shoulder room, and you pay more for bedding, since Cal King linens are a smaller retail category.
Split King (two Twin XL)
The footprint matches a King, yet this version solves three problems at once: independent head and foot articulation on an adjustable base, a different firmness per side, and carrying that two people can actually manage. Two 38-inch halves go up a staircase that a solid 76-inch King cannot. Then there is the seam down the middle. A foam gap filler and a split-king fitted sheet set handle most of it, though not all.
Will it actually fit the bedroom?
Mattress size is not the number that matters. Frame footprint is. Most platform beds add 2–4 inches per side, and headboards add another 2–5 inches of length.
Work from this: room width ≥ mattress width + 60 inches, which gives a 30-inch walkway on each side. Drop under 24 inches of walkway and you will be shuffling sideways past the bed in the dark.
| Size | Typical frame footprint | Workable room | Comfortable room |
|---|---|---|---|
| King | 80 × 84 in | 10 × 12 ft | 12 × 12 ft |
| California King | 76 × 88 in | 10 × 13 ft | 12 × 13 ft |
| Split King on adjustable base | 80 × 84 in + 6 in rear clearance | 10 × 12.5 ft | 12 × 13 ft |
Two checks people skip: a King centered on a wall leaves no clearance for a swinging closet door on that wall, and nightstands want 20–24 inches each, which comes out of the walkway rather than the mattress.
The stairwell test: three measurements, five minutes
Because a King mattress travels on edge, its thickness (10–15 in) clears any standard 30-inch door. Turns are what stop deliveries. Run through this before you check out:
- Narrowest clear width. Measure every doorway, hallway and stair run at its tightest point, handrails and trim included. The International Residential Code requires only 36 inches of clear stair width (R311.7.1), and houses built before 1940 often have less.
- Corner sum. At each 90° turn, add the width of the hallway to the depth of the landing. Under 82 inches, a solid 76-inch King will not pivot. Under 90 inches, expect scraped drywall.
- Vertical clearance at the turn. Sloped ceilings above a stair landing are the classic failure point. Swinging the mattress upright takes roughly 78 inches of headroom.
- Boxed or flat? Compressed-in-a-box mattresses, meaning most all-foam models and many hybrids, arrive as a 20 × 20 × 42-inch carton and make step 2 irrelevant. Premium innersprings delivered white-glove and uncompressed do not.
- Foundation, too. A one-piece King box spring measures 76 × 80 inches and does not flex. Order a split foundation (two 38 × 80 halves) if any answer above came out tight.
Two or more borderline measurements? Buy Split King. Calling it a compromise misses the point: it is the version of this size that fits real houses.
US vs Canada vs UK: why "king" means three things
Anyone searching "king size mattress US" or "king size mattress USA" is usually comparing against a non-US standard. Canada matches the US exactly. The UK does not, because its sizes follow a separate convention maintained by the National Bed Federation.
| Name | Market | Size | Closest US equivalent |
|---|---|---|---|
| King | US / Canada | 76 × 80 in | — |
| King | UK / Ireland | 150 × 200 cm (59 × 79 in) | Roughly a US Queen |
| Super King | UK / Ireland | 180 × 200 cm (71 × 79 in) | 5 in narrower, 1 in shorter than US King |
| Emperor | UK (specialist) | 200 × 200 cm | Wider than US King |
Practical consequence: UK bedding will not fit a US King, and UK Super King sheets end up loose in width and short in nothing. Buy linens in the market where you bought the mattress.
Columbus-specific notes
In German Village, Victorian Village and Olde Towne East, stair turns regularly land in the 70-inch corner-sum range, often with a quarter-turn landing under a sloped ceiling. Clintonville and Grandview Heights houses from the 1920s frequently come with 32-inch stair widths. Short North condos usually have an elevator to solve it, so check the cab depth, since a 76-inch mattress needs a diagonal fit. When in doubt, ask the retailer for a boxed shipment or a split foundation before delivery day. Not after.
Частые вопросы
Is a California King bigger than a King?
Longer, not bigger. Cal King works out to 6,048 square inches against the King's 6,080. Each sleeper gets 36 inches of width instead of 38, plus 4 inches of extra length.
Can I use King sheets on a Split King?
Flat sheet, duvet and comforter, yes. Fitted sheet, no. That takes two Twin XL fitted sheets, or a split-king set. On a base that articulates, standard sheets pop off the corners as soon as the head raises.
Will a King mattress fit through a 30-inch doorway?
Yes. Carried on edge, only the thickness (10–15 in) has to pass through. The risk lives in turns and landings, not door width.
Do I need a special frame for a Split King?
Any King frame works, though the two halves need either two Twin XL foundations or two Twin XL adjustable bases. Confirm that the frame's interior measures 76 inches wide, not 76 inches outside-to-outside.
What is the minimum bedroom size for a King bed?
10 × 12 feet is workable with one nightstand and a 24-inch walkway. 12 × 12 feet is comfortable with nightstands on both sides. For Cal King, add a foot of length.
Автор: MattressMart Columbus Editorial. Обновлено: 2026-09-09