A standard US king size mattress is 76 inches wide and 80 inches long (193 × 203.2 cm). That gives you 6,080 square inches of sleep space. It is the widest of the common US mattress sizes.
Many shoppers mix up the king size bed dimensions with other sizes. A 78 × 72, a 6 × 7, and a 60 × 80 are not kings. This guide shows the exact king mattress size, how it compares, and how to make sure it fits your room.
Table of Contents
King Size Mattress Dimensions (Exact Size)
What is the exact size of a king size mattress? It is 76″ × 80″. Wikipedia’s bed size table lists the length as 79.5 inches, and brands often round it up to 80. Expect a variation of about half an inch.
| Measure | Imperial | Metric |
|---|---|---|
| Width | 76″ | 193 cm |
| Length | 80″ | 203.2 cm |
| Surface area | 6,080 sq in | n/a |
| Min. room size | 12′ × 12′ | 3.66 m × 3.66 m |
How big is a king size mattress for two people? Each sleeper gets about 38 inches of width. That equals the width of a twin. A queen gives each person only 30 inches.
The king-size bed rose in popularity in the mid-20th century, according to BedInABox. Today it is the go-to standard king mattress size for couples who want space.
King vs Queen vs California King Size
The size chart below shows where the king sits. These are the standard US mattress sizes, with figures from Turmerry.
| Size | Dimensions (W × L) | Min. room |
|---|---|---|
| Twin | 38″ × 75″ | 7′ × 10′ |
| Twin XL | 38″ × 80″ | 7′ × 10′ |
| Full | 54″ × 75″ | 9′ × 10′ |
| Queen | 60″ × 80″ | 10′ × 10′ |
| King | 76″ × 80″ | 12′ × 12′ |
| California king | 72″ × 84″ | 12′ × 12′ |
What is the difference between a king and a queen? A king is 16 inches wider than a queen. Both are 80 inches long. By area, the king has 1,280 more square inches.
Just as choosing the right king mattress requires accurate measurements for a comfortable fit, planning a sports space also depends on getting the dimensions right. If you’re setting up a recreational area, understanding standard pickleball court dimensions and space requirements can help you make the most of your available space.
What is the difference between a king and a California king? The Cal king is 4 inches narrower and 4 inches longer. That makes it a better fit for tall sleepers. Their surface areas are almost the same (6,080 vs 6,048 sq in).
A quick check:
- Choose a king if you want width, or you share the bed with a partner, a child, or a pet.
- Choose a Cal king if you are over 6’2″ or your room is long and narrow.
- Choose a queen if the room is smaller than 12′ × 12′.
King Size Bed Fit: Room, Frame and Bedding
How big does a room need to be for a king size bed? Plan for 12′ × 12′ at minimum. Some guides quote a smaller figure, but 12 × 12 leaves real walking space. In a room that size, the bed leaves about 68 inches on the width side and 64 inches at the foot.
Leave about 24 inches of clearance on the sides and foot. This lets you walk, make the bed, and open drawers.
A king size bed frame is larger than the mattress. Turmerry lists frames at about 78–81″ × 82–85″. Measure the frame, not just the mattress.
Check these before you order:
- Doors and halls: A 76-inch mattress is wide. Measure doorways, stairs, and turns.
- Nightstands: Allow space for them on both sides.
- Room shape: In a rectangular room, put the headboard on the shortest wall. In an L-shaped room, keep the bed in the main block of the room.
- Bedding: Buy king sheets. Check the pocket depth if you add a topper.
- Base: An adjustable base or foundation must match the king (or split king) size.
Turmerry’s guide lists king mattress prices of about $800 to $2,000 for standard builds. Prices vary by brand, material, and sale.
Other King Variants and Split King Sizes
What is a split king mattress? It is two twin XL mattresses (38″ × 80″ each) placed side by side. Together they measure 76″ × 80″, the same as a standard king. Partners can pick different firmness levels, and each side can move on an adjustable base.
King-size variants are less common. Here are the sizes listed by Turmerry and BedInABox:
| Variant | Dimensions | Room needed |
|---|---|---|
| Super king | 72″ × 78″ | about 12′ × 12′ |
| Wyoming king | 84″ × 84″ | larger room |
| Vermont king | 96″ × 96″ | larger room |
| Texas king | 80″ × 98″ | 14′ × 16′ |
| Alaskan king | 108″ × 108″ | 14′ × 16′ |
These need special sheets and frames. Many stores do not stock them.
Sizes also change by country. A UK king is 150 × 200 cm, about 59″ × 79″. That is close to a US queen. A UK super king is 180 × 200 cm. Check the country and the unit on any foreign listing.
King Size Mattress Dimensions FAQs
Is 78 × 72 king size?
No. A US king is 76 × 80. A mattress with a 72-inch side is closer to a California king (72 × 84) or a rare super king (72 × 78). Measure the bed before you buy sheets or a frame.
What is the exact size of a king-size bed?
It is 76 inches wide by 80 inches long (193 × 203.2 cm). Some brands list the length as 79.5 inches.
Is 6 by 7 king size?
No. Six feet by seven feet is 72″ × 84″, which is a California king. A standard king is 6’4″ × 6’8″.
Is a king bed 60 by 80?
No. A 60″ × 80″ mattress is a queen. A king is 76 inches wide.
Conclusion
The standard king size mattress dimensions are 76″ × 80″. Measure your room, the frame, and the path to the bedroom before you order. Aim for at least 12′ × 12′ and 24 inches of clearance.
Rehmaan Khan is a Measurement Content Researcher Specializing in MLmeasurement, Size Guides, Charts, and Simple Educational Measurement Content.