A king mattress is 76 in wide and 80 in long, or 6 ft 4 in by 6 ft 8 in: as wide as two twin XL mattresses side by side, and as long as a queen. It’s also called an Eastern king. A frame adds about 1 to 6 in each way. With 24 in of floor on both sides and past the foot, a king needs a headboard wall of at least 10 ft 8 in.
King bed dimensions
| Measure | Inches | Feet | Centimeters |
|---|---|---|---|
| Width | 76 in | 6 ft 4 in | 193 cm |
| Length | 80 in | 6 ft 8 in | 203 cm |
| Mattress area | 6,080 sq in | 42.2 sq ft | 3.9 m² |
| Thickness | 8 to 14 in; 10 to 12 most common | – | 20 to 36 cm |
| Bed frame, outside | about 77 × 82 to 82 × 85 in | – | about 196 × 208 to 208 × 216 cm |
Width and length: Sleep Foundation, Sealy, Mattress Firm, Saatva, Purple, Casper, Tempur-Pedic and Nolah all give 76 × 80 in. Thickness: Sleep Foundation. Frames: the makers’ product pages below. Feet and centimeters are conversions.
A king gives two sleepers 38 in each, the width of a twin XL, against 30 in each on a queen. For a couple who want more room, or share the bed with a child or a pet, that’s the step up.
King, California king or split king?
| Bed | Width × length | Good to know |
|---|---|---|
| King (Eastern king) | 76 × 80 in | The standard king; the most frames, sheets and choices |
| California king | 72 × 84 in | 4 in narrower and 4 in longer, for tall sleepers and narrow rooms |
| Split king | 76 × 80 in as two 38 × 80 in | Two twin XLs on one frame, so each side can differ in firmness or move on an adjustable base |
| Split California king | 72 × 84 in as two 36 × 84 in | Fewer brands offer it |
| Queen | 60 × 80 in | 16 in narrower, same length |
Sizes from Sleep Foundation, Saatva, Sealy, Mattress Firm and Tempur-Pedic.
The king vs California king guide shows both in real rooms. A king is not two standard twins: two twins make 76 × 75 in, 5 in short of a king’s length, so a split king uses twin XLs. Bigger than all of these: the Texas, Wyoming and Alaskan kings.
How much bigger is a king bed frame?
The frame is what takes up your floor. A bare metal platform is about the size of the mattress; wood and upholstered frames add a few inches, and a frame with a headboard and wide rails up to about six. Three real king frames, measured outside by their makers:
| Frame | Outside, W × L | Over the mattress |
|---|---|---|
| Zinus Allen (wood platform) | 76.7 × 82.1 in | about 1 in wider, 2 in longer |
| Zinus Dachelle (upholstered) | 78.4 × 84.4 in | about 2 in wider, 4 in longer |
| IKEA MALM (headboard and footboard) | 82¼ × 83⅛ in | 6¼ in wider, 3⅛ in longer |
Outside sizes from each maker’s product page, October 2026. Over the mattress: against a 76 × 80 in king.
Our bedroom layout planner uses 80 × 84 in for a king frame, and you can type in your own.
How much room a king bed needs
Enter your room’s two walls. The check centers a king on the headboard wall and looks for 24 in on both sides and past the foot, the planner’s standard setting.
24 in beside the bed and past its foot, the planner’s standard setting.
The headboard wall needs 80 + 24 + 24 = 128 in (10 ft 8 in), and the room needs 109 in from that wall to the one opposite. In a 10-foot-wide room a king fits only with one side against the wall. The room size for a king bed guide has the plans, from a 10×11 up.
Will a king mattress measure exactly 76 × 80?
Close, but often not to the inch. Serta lists its king as 76 × 79.5 in, and IKEA’s MALM king frame takes a 76 × 79½ in mattress. Frames and sheets are made for the nominal size, so half an inch doesn’t matter. Thickness varies far more, from 8 to 14 in, so check a fitted sheet’s pocket depth against your mattress.
Questions
How wide is a king size bed?
A king mattress is 76 in wide, 6 ft 4 in. The frame is about 77 to 82 in wide, depending on its rails and headboard.
How long is a king bed?
80 in, or 6 ft 8 in, the same as a queen. A California king is 84 in long.
What is the size of a king bed in feet?
6 ft 4 in wide by 6 ft 8 in long, about 42 square feet of mattress.
Is a king the same as two twin beds?
Not quite. Two twins side by side are 76 × 75 in, as wide as a king but 5 in shorter. Two twin XLs make exactly a king, 76 × 80 in: that’s a split king.
Which is bigger, a king or a California king?
Neither overall: a king is 4 in wider (76 in against 72 in), and a California king is 4 in longer (84 in against 80 in). The king has slightly more mattress: 6,080 square inches against 6,048.
How much bigger is a king than a queen?
16 in wider, 76 in against 60 in, and the same 80 in long: about 42 square feet of mattress against 33⅓.
How big is a king bed frame?
About 77 to 82 in wide and 82 to 85 in long outside, from a bare platform (Zinus Allen) to a frame with a headboard and footboard (IKEA MALM).
How big is a king bed in cm?
The mattress is 193 × 203 cm, 76 × 80 in converted.
Sources
- Sleep Foundation, king size bed dimensions: king 76 × 80 in, California king 72 × 84 in
- Sealy, the ultimate mattress size guide and Mattress Firm, mattress sizes: king, California king, and a split king from two twin XLs
- Saatva, guide to mattress dimensions and Tempur-Pedic, split king: split king and split California king sizes
- Maker product pages: Zinus Allen, Zinus Dachelle, IKEA MALM: outside sizes
- Sleep Foundation, how thick should a mattress be: 8 to 14 in, 10 to 12 in most common
- Serta, mattress sizes and dimensions: king 76 × 79.5 in as sold
Sizes checked October 20, 2026. Room sizes are from our bedroom layout planner. Feet, centimeters and areas are conversions.