Quick answer
How big is a king mattress?
76" × 80" (10" thick) — A king mattress is 76 inches wide and 80 inches long — the widest standard mattress. Each sleeper gets 38" of personal space (equal to a twin bed).
Measurements
Dimensions.
- 76"
- Width
- 80"
- Length
- 10"
- Height
Doorway fit
Will a King Mattress fit through a doorway?
Will fit through with proper technique. Smallest dimension (thickness): 10". Standard interior door: 32". Standard exterior door: 36".
Fits with room to spare
Fits with room to spare
Fits with room to spare
Mattress size comparison
| Size | Width | Length | Area |
|---|---|---|---|
| Twin | 38" | 75" | 2,850 sq in |
| Twin XL | 38" | 80" | 3,040 sq in |
| Full/Double | 54" | 75" | 4,050 sq in |
| Queen | 60" | 80" | 4,800 sq in |
| King ← | 76" | 80" | 6,080 sq in |
| Cal King | 72" | 84" | 6,048 sq in |
Measure smart
What to measure.
Four numbers decide nearly every fit check. Get these right and the rest follows.
- 01Width, depth, and height of the item at its widest points, including feet, arms, handles, and headboards.
- 02The clear opening of the space, not the frame. A 36-inch door gives roughly 32 inches once the door and stops are accounted for.
- 03The item's smallest dimension. It decides whether tilting or turning it on its side gets it through.
- 04Diagonal clearance at turns, landings, and corners, where the real bottleneck usually is.
Don't make these
Common mistakes.
Most “it didn't fit” stories trace back to one of these oversights.
- ⚠Measuring the door frame instead of the clear opening, then losing two inches you assumed you had.
- ⚠Forgetting that feet, arms, and handles add to the nominal size printed on the box.
- ⚠Treating a soft mattress and a rigid frame the same. One compresses, the other does not.
- ⚠Planning the doorway but ignoring the turn at the top of the stairs.
Go deeper
Related items and calculators.
Frequently asked
Questions we keep getting.
Will a king mattress fit through a standard doorway?
It's tight but possible. At 76" × 80" × 10", the 10" side passes through a 32" door, but the 76" width makes cornering difficult. Use the front/exterior door (36") and remove door stops for best results.
01What is the minimum room size for a king bed?
A king bed needs at least a 12' × 12' room (144 sq ft) for comfortable walkways and nightstands. In a 10' × 12' room it will fit but feel cramped.
02What is the difference between king and California king?
King is 76" × 80" (wider); Cal king is 72" × 84" (narrower but longer). King is better for couples who want more width; Cal king suits taller individuals who need extra length.
03