Bed and Mattress Sizes Compared: Twin to California King

A king size bed measures 76 by 80 inches. A twin measures 38 by 75 inches. That’s the entire size range in one sentence — everything else is detail.

This guide covers every standard mattress size in inches and centimeters. You’ll also get width-per-person math, room-fit guidance, and the real trade-offs between full vs. queen and king vs. California king.

Bed and Mattress Size Chart (Inches and Centimeters)

Six sizes cover nearly every bed sold in the US. Here’s how they stack up.

Twin XL is just a twin with 5 extra inches of length. That’s why it’s the standard dorm-room size — tall students need the legroom.

Full and Double are the same mattress. Retailers use both names, but the dimensions never change: 54 by 75 inches.

Why These Six Sizes Exist

Mattress sizes weren’t designed from scratch. Most grew out of standard bedding and bed-frame dimensions set decades ago.

Twin got its name because two of them, pushed together, sleep a couple — the “twin” setup. Full later became the default for one adult before queen took over.

Queen and king arrived later as beds got wider to fit growing average body sizes. California king came out of a regional preference for a longer, narrower profile.

Manufacturers still build to these six sizes today. That’s why sheets, frames, and mattress pads are labeled by name instead of raw dimensions.

Width Per Person: How Much Space You Actually Get

A twin fits one sleeper. Two adults sharing anything smaller than a queen will feel it.

Split a full bed’s 54-inch width between two people and each person gets 27 inches. That’s narrower than a standalone twin.

A queen gives each person 30 inches — still tight, but workable for most couples.

A king splits to 38 inches per side. That’s the exact width of a twin mattress, per person. It’s the most common upgrade pick for couples who feel cramped in a queen.

Full vs. Queen: What 6 Inches Buys You

A queen is 6 inches wider than a full (60 vs. 54) and 5 inches longer (80 vs. 75).

That 6 inches matters more than it sounds. Split between two sleepers, it adds 3 inches of elbow room on each side.

The extra 5 inches of length also matters for anyone over 5’10”. A full’s 75-inch length gets tight fast for a taller sleeper.

Full beds fit smaller bedrooms and single sleepers well. Queens are the default choice for couples and for guest rooms meant to sleep two.

King vs. California King: Two Different Trade-offs

A king is 76 by 80 inches. A California king is 72 by 84 inches — 4 inches narrower, 4 inches longer.

Here’s the catch: king actually has more total surface area. Multiply it out — king is 6,080 square inches, Cal king is 6,048 square inches. King wins by 32 square inches, despite being the “shorter” one.

So the choice isn’t about total size. It’s about which dimension you need more.

Choose California king if you’re taller than 6’2″ and need the extra 4 inches of length. Choose king if you and a partner want maximum shared width.

One more fact worth knowing: a king bed is exactly two Twin XL mattresses pushed together. Two 38-inch widths add up to 76 inches — a king, to the inch. That’s the “split king” setup, and it explains why some king bed frames come in two pieces.

Matching Mattress Size to Sleeper Height

Standard mattresses run 75 inches long. That fits comfortably up to about 6 feet tall, with a few inches to spare.

Above 6 feet, that margin shrinks fast. A 6’2″ sleeper on a 75-inch mattress has just 2 inches of clearance — tight enough that feet can hang off the end.

Twin XL, queen, king, and California king all solve this differently. Queen and king run 80 inches long, the same length as Twin XL.

Only California king stretches to 84 inches. For sleepers over 6’3″, that extra 4 inches is often the deciding factor over a regular king.

Room Size Fit Guidance

Bed size alone doesn’t tell you if a mattress fits your room. You also need clearance to walk around it and open dresser drawers.

A common guideline: leave at least 24 to 30 inches of open floor space on each side you walk past.

• Twin: fits comfortably in a 7 x 10 ft room
• Full: needs roughly 9 x 10 ft
• Queen: needs roughly 10 x 10 ft, more with a footboard
• King: needs roughly 12 x 12 ft minimum
• California king: needs roughly 12 x 12 ft, plus extra length clearance

A king in a 10 x 10 ft room leaves almost no walking space. Measure your room before you measure the mattress.

Don’t forget the hallway and stairwell on delivery day. A king mattress is 76 inches wide — wider than most standard doorways, which run 32 to 36 inches.

Most king and California king mattresses ship compressed and rolled for exactly this reason. Check delivery specs before you buy if your stairwell is narrow.

Common Mistakes to Avoid

Buyers often assume California king is the bigger bed overall. It isn’t — king has 32 more square inches of surface, as shown above.

Another mix-up: people buy “full” sheets thinking they need something different from “double” sheets. They’re identical. Both fit a 54 x 75-inch mattress.

Some shoppers also confuse Twin XL with Twin, then buy sheets that are 5 inches too short. A standard twin sheet won’t stretch over an 80-inch Twin XL mattress — the fitted corners simply won’t reach.

A fourth mistake: assuming a “split king” and a regular king use the same sheets. They don’t. A split king is two separate 38 x 80-inch mattresses, so it needs two twin XL fitted sheets, not one king sheet.

Frequently Asked Questions

What size is a twin bed?
A twin bed is 38 inches wide and 75 inches long. It’s the smallest standard mattress size, built for one sleeper.

How big is a king size bed?
A king size bed is 76 inches wide and 80 inches long — 193 by 203.2 centimeters. It’s the widest standard mattress made.

What are the dimensions of a full size mattress?
A full mattress measures 54 by 75 inches, or 137.2 by 190.5 centimeters. It’s also sold as a “double.”

Is California king bigger than king?
Not overall. California king is longer (84 vs. 80 inches) but narrower (72 vs. 76 inches). King actually has more total square inches.

How much bigger is a queen than a full?
A queen is 6 inches wider and 5 inches longer than a full — 60 x 80 inches versus 54 x 75 inches.

What size is a twin XL bed?
A Twin XL is 38 inches wide and 80 inches long — same width as a regular twin, 5 inches longer. Two of them side by side equal one king.

How many inches wide is a queen size bed?
A queen bed is 60 inches wide. That splits to 30 inches per person for a couple sharing the mattress.

What is the difference between a double and a full bed?
There isn’t one. Double and full describe the same 54 x 75-inch mattress. Retailers just use different names for the same product.

How many inches is a king size bed in total?
A king bed measures 76 inches wide by 80 inches long. Combined, that’s 6,080 square inches of sleeping surface — the largest of any standard size.