A standard king size mattress is 76 inches wide and 80 inches long (193 × 203 cm). That is about 6 feet 4 inches by 6 feet 8 inches.

Height, frame size, and room fit matter too. This guide covers all of them, plus Cal King, split king, and other king bed dimensions in the USA.

King Size Mattress Dimensions: Width, Length and Height

What are the dimensions of a king size mattress? Here is the quick answer.

Measure	Inches	Centimeters
Width	76″	193 cm
Length	80″	203 cm
Surface area	6,080 sq in	n/a
Height (thickness)	10″ to 15″ (typical)	25 to 38 cm

King mattress width is the big win. It is 16 inches wider than a queen. Each sleeper gets about 38 inches, the same as a twin bed.

King mattress length is 80 inches, the same as a queen. Sleepers over 6 feet 4 inches may want more legroom.

King mattress height has no set standard. Most mattresses run 6 to 18 inches tall, and most fall between 10 and 15. Thin models are around 8 to 10 inches. Thick pillow-top and hybrid beds go past 13.

Tall mattresses need deep-pocket fitted sheets. They also raise the bed, so check how high your bed frame sits.

The actual size of a king mattress varies a little. The International Sleep Products Association lists 76 × 79.5 inches. Brands round up to 80. Expect a difference of half an inch to an inch.

King vs. California King and Other King Sizes

“King” is a family of sizes. Compare them before you buy.

Size	Dimensions	Surface Area
King (Eastern King)	76″ × 80″	6,080 sq in
California King (Western King)	72″ × 84″	6,048 sq in
Split King	Two 38″ × 80″ halves	6,080 sq in
King RV	72″ × 79.5″	5,724 sq in
Wyoming King	84″ × 84″	7,056 sq in
Texas King	80″ × 98″	7,840 sq in
Alaskan King	108″ × 108″	11,664 sq in

California King

A California king is 4 inches narrower and 4 inches longer than a standard king. The floor space is almost the same. It suits tall sleepers and narrow rooms.

The size is older than you might think. Industry research shows it dates to the 1920s, when it was made for Hollywood stars.

Split King

A split king is two Twin XL mattresses side by side. Each half is 38 × 80 inches. It works well with an adjustable bed base. Each sleeper can also pick their own firmness level.

Texas King and Alaskan King

These are oversized mattresses. They are often custom-made. Bed frames and sheets are harder to find, and they need a very large room.

Shopping tip: Sizes change by country. A UK king is 60 × 78 inches, close to a US queen. An Australian king is 72 × 80. Check the numbers on imported beds.

Must Visit: Queen Mattress Dimensions: Standard Size, Friendly Guide (2026)

King Size Bed Frame and Room Size Needs

A king bed frame is usually 0.5 to 2 inches bigger than the mattress. Most frames stand 16 to 24 inches tall. Platform beds often sit lower.

How big should a room be for a king bed? Leave about 24 inches of walking space on both sides and at the foot. Here is the math:

• Width: 76″ + 24″ + 24″ = 124 inches (about 10 feet 4 inches)
• Length: 80″ + 24″ = 104 inches (about 8 feet 8 inches)

Dressers and nightstands add more. So a 12 × 12 foot room is the comfortable pick. A 10 × 12 foot room is the tight minimum.

Place the bed on the longest wall. This keeps both sides open. It also keeps closets and doors clear.

Plan the delivery, too. Measure doors, hallways, and stairwells. A boxed foam king can weigh about 110 pounds.

Remember your king size bedding. Sheets, comforters, and mattress protectors all cost more than queen sizes.

Is a King Size Mattress Right for You?

A king is a strong fit for:

• Couples who like space
• Families who share the bed with kids or pets
• People who sprawl or change positions often

A king may not fit if:

• Your bedroom is smaller than about 10 × 12 feet
• You sleep alone and want to save money
• You move homes often

Cost is a real factor. More material and labor go into a king. Frames and bedding follow the same pattern.

Quick check: measure the room, count the sleepers, pick a height, then set a budget.

King and queen sizes are fairly new. Mattress makers introduced them in the mid-1940s, and they took off in the 1950s and 60s.

FAQs

Is 76×80 king size?

Yes. 76 × 80 inches is the standard US king size. A bed that is 72 × 84 inches is a California king.

Is a king bed 60 by 80?

No. That is a queen. A king is 76 inches wide, which is 16 inches wider.

What is the actual size of a king-size bed?

The mattress is about 76 × 80 inches. The industry standard is 76 × 79.5. The bed frame is slightly larger, often by 0.5 to 2 inches.

Is a full two twins?

No. A full is 54 inches wide. Two twins side by side make 76 inches. That is closer to a king.

Can I put two twin beds together to make a king bed?

Not quite. Two standard twins (38 × 75) make a bed 76 inches wide and only 75 inches long. That is 5 inches shorter than a king.

Two Twin XL mattresses (38 × 80) match a king exactly. That setup is a split king. Use a king-size frame or a connector to stop the gap and drift.

Can two adults sleep in a full bed?

Yes, but it is tight. Each person gets about 27 inches. A crib mattress is 28 inches wide. Most couples do better on a queen or larger.

Final thoughts

Standard king size mattress dimensions are 76 × 80 inches. Match that size to your room, your height, and your budget, and the choice gets easy.