King Size Mattress Dimensions: Size, Fit & Room Needs
A king size mattress measures 76 inches wide by 80 inches long — about 6 feet 4 inches across and 6 feet 8 inches long, or roughly 193 x 203 cm. That makes it the widest standard mattress size sold in the United States, and the size most couples move to when a queen starts feeling tight. Below are the exact king size mattress dimensions, how a king compares to a queen, a California king and a split king, and what to check in your bedroom before you order one.
King Size Mattress Dimensions at a Glance
| Measurement | Inches | Feet | Centimeters |
|---|---|---|---|
| Width | 76" | 6' 4" | 193 cm |
| Length | 80" | 6' 8" | 203 cm |
| Surface area | 6,080 sq in | ~42.2 sq ft | ~3.92 sq m |
You will also see a king called an Eastern king or a standard king. All three names refer to the same 76" x 80" mattress. Height is the one dimension that is not standardized — profiles vary widely by model — so check the spec sheet for the mattress you are considering.
Space per sleeper
Split evenly, two people on a king each get 38 inches of width — the same width as a twin XL mattress. That is the practical reason a king feels so different from a queen: on a queen, each person has 30 inches. Eight extra inches per sleeper is enough to keep elbows, knees and a co-sleeping pet from turning into a nightly negotiation.
How a King Compares to Other Mattress Sizes
| Size | Dimensions | Compared to a king |
|---|---|---|
| Twin | 38" x 75" | Half the width, 5" shorter |
| Twin XL | 38" x 80" | Half the width, same length |
| Full | 54" x 75" | 22" narrower, 5" shorter |
| Queen | 60" x 80" | 16" narrower, same length |
| King | 76" x 80" | — |
| California King | 72" x 84" | 4" narrower, 4" longer |
| Split King | Two 38" x 80" halves | Same footprint, two pieces |
King vs. queen
A king is 16 inches wider than a queen and exactly the same length. If your complaint is elbow room, a restless partner or kids climbing in, a king solves it. If your complaint is your feet hanging off the end, it does not — both are 80 inches long, and you want a California king. Queen is still the better call in bedrooms under about 10 feet wide, which is why it is the size most king shoppers are stepping up from.
King vs. California king
This trips up a lot of shoppers: a California king is not bigger than a king, it is shaped differently. At 72" x 84", a Cal king trades 4 inches of width for 4 inches of length, and it actually has slightly less total surface area than a standard king. Choose a Cal king if someone in the bed is roughly 6'2" or taller, or if your bedroom is long and narrow. Choose a standard king for maximum shoulder room. Our California king mattresses are stocked alongside standard kings so you can lie on both back to back.
King vs. split king
A split king is a king-size footprint made of two twin XL mattresses, 38" x 80" each, placed side by side. Total dimensions are the same 76" x 80". The reason to split it is independent adjustment: each half can sit on its own adjustable base so one person can raise their head to read while the other stays flat, and each person can pick a different firmness. The trade-off is a seam down the middle, which most couples bridge with a mattress pad or a gap filler. If an adjustable base is part of your plan, start with our split king mattresses.
What Room Size Do You Need for a King?
A king occupies roughly 42 square feet of floor before you add a frame, which typically adds a few inches on each side. A widely used interior design rule of thumb is to leave about 24 to 30 inches of clear walking space on both sides and at the foot of the bed. Run that math and a 10' x 12' bedroom is generally considered the practical minimum for a king; 12' x 12' or larger is comfortable, and anything smaller usually means walking sideways past the footboard.
Before you commit, measure three things:
- Wall to wall. Subtract 76 inches plus your frame's overhang from the headboard wall.
- Door and window swing. Confirm the bed will not block a closet door or a window you open.
- Nightstands. Two nightstands plus a king runs close to 10 feet of wall. Narrower rooms work better with a queen, or with one nightstand.
Getting a King Into Your Home
A king mattress is a single 76-inch-wide piece, and that width is what causes delivery problems, not the weight. Measure the narrowest point on the path to the bedroom: doorway widths, hallway turns, and especially the landing at the top of a staircase. Older LA homes, Glendale apartments and Craftsman-style houses with tight stair turns are the usual culprits.
Two things make this easier. Many all-foam and hybrid mattresses ship compressed in a box, which changes the shape you have to maneuver, and a split king arrives as two 38-inch halves that will go almost anywhere a twin XL will go. If the path is tight, tell us before delivery and we will look at the route with you.
Foundations, Frames and Bedding for a King
A few things change when you size up to a king:
- Center support is not optional. A 76-inch span needs a frame with a center rail and at least one center leg touching the floor. Without it the mattress sags in the middle and the warranty may be affected.
- King foundations often come in two pieces. Many king box springs and foundations are sold as two 38" x 80" halves, which is a genuine advantage in a tight stairwell.
- Buy king sheets, not "king or Cal king." They are different cuts. A standard king fitted sheet is made for 76" x 80"; a Cal king sheet is 72" x 84" and will be too narrow and too long.
- Two king pillows fit the width almost exactly. King pillows run about 36 inches long, so a pair spans roughly 72 inches of a 76-inch mattress.
If you want every size laid out side by side, our mattress dimensions and size guide has the full chart.
Who a King Is Right For
A king makes the most sense if you share the bed and either of you moves a lot at night, if kids or pets regularly end up in it, or if you each want a different firmness or adjustable base position — that last one points to a split king. It makes less sense if your room is under about 10 feet wide, or if the taller sleeper's height is the real problem, which is a California king question.
King Size Mattress FAQ
What are the exact dimensions of a king size mattress?
76 inches wide by 80 inches long, or 6'4" x 6'8" (about 193 x 203 cm). Height varies by model and is not standardized.
Is a king the same as an Eastern king?
Yes. "Eastern king" and "standard king" both mean 76" x 80". The term exists mainly to distinguish it from a California king, which is 72" x 84".
Will two twin XL mattresses make a king?
Yes. Two twin XL mattresses at 38" x 80" each come to exactly 76" x 80" — that is what a split king is. You will want a split king sheet set or a bridging pad to smooth the center seam.
Do king and California king sheets fit both beds?
No. Fitted sheets are cut to the mattress. King sheets are made for 76" x 80" and California king sheets for 72" x 84". Flat sheets and comforters are more forgiving, but fitted sheets are not interchangeable.
Can a king mattress fit up a standard staircase?
Usually, but the tight spot is the turn or landing, not the stair width. Measure the narrowest point of the whole route. If it is close, a split king or a mattress that ships compressed in a box is the safer choice.
See a King in Person in Glendale
Dimensions on a screen only get you so far — 76 inches of width feels different once you are lying on it. Our Glendale showroom has kings, California kings and split kings set up so you can compare them side by side, and we serve shoppers across Los Angeles, Burbank and Pasadena. Browse our king mattresses online or come in and take your time.
Every mattress we sell comes with a 120-night sleep trial, and we offer free delivery and setup across the LA area, plus a 90-day price match and 0% APR financing. If you are not sure whether a king or a California king fits your room, bring your measurements and we will work it out with you.