Mattress Sizes: Every US Dimension, in Inches

There are six standard mattress sizes sold in the United States. Width and length are standardised across the industry — a Queen is 60 by 80 inches whoever makes it. Here is the complete table, width first:

Those are the standard sizes. Two caveats before you buy anything against them.

The numbers are standard. The mattress might not be.

Width and length are standardised, but individual products drift by an inch or so either way — manufacturing tolerance, a thick quilted cover, a slightly generous cut. It rarely matters for fitted sheets, which have elastic and forgiveness built in. It can matter for a tight bed frame or a fitted storage platform, where an extra inch of mattress meets a wooden rail that has no opinion about tolerance.

So: measure your frame, not your assumptions.If you are buying a mattress for a frame you already own, measure the interior of the frame before you order, and check the mattress listing's own stated dimensions rather than trusting the size name. If you are buying both, buy the mattress first and let the frame follow it.

And the number that is not standardised at all is thickness. Height runs from roughly 8 inches to 15, it varies by model rather than by size, and it is the one dimension the size name tells you nothing about. It matters for two practical reasons: deep-pocket sheets, and whether you can comfortably sit on the edge with your feet on the floor.

How to choose: three questions, in this order

1. Who is actually in the bed?

Not who sleeps there tonight — who sleeps there over the life of the mattress, which is likely to be a decade. Count the dog. Count the toddler who will be arriving at 5am for the next four years. Sharing a bed is a width problem, and width is the dimension people under-buy.

Do the arithmetic per person. A Full at 54 inches gives two adults 27 inches each — less than a Twin, which is 38. A Queen gives each person 30 inches. A King gives each person 38 inches, which is a full Twin apiece and the reason a King feels transformative rather than merely larger. If two adults share a bed nightly and the room can take it, a King is the size most people wish they had bought.

2. How tall is the tallest person in it?

This is the question the length column answers, and it is simpler than the marketing makes it. A 75-inch mattress is 6 feet 3. A 80-inch mattress is 6 feet 8. An 84-inch Cal King is 7 feet.

You want roughly 4 to 6 inches of clearance beyond your height so your feet are not hanging over the edge and your pillow is not being pushed off the top. In practice: under about 5'10", a 75-inch bed (Twin or Full) is fine. Over that, you want the extra 5 inches — which is precisely what Twin XL, Queen and King give you over Twin and Full. Over about 6'2", look seriously at a California King, because it is the only standard size that goes past 80 inches.

3. How big is the room?

Leave 24 to 30 inches of clear floor on any side you need to walk down, and remember the frame is typically 2 to 5 inches larger than the mattress in each direction. Then open the doors — a bed that fits the floor plan but blocks a wardrobe, a radiator or the swing of the bedroom door is the wrong bed. Measure the stairwell and the turn at the top too if you live above the ground floor. This is a real advantage of a bed in a box: it arrives compressed and goes round a corner that a traditional King never would.

King vs California King: the only distinction that matters

This is the most misunderstood pair in the list, and the fix is one sentence: a King is wider, a California King is longer.

A King is 76 by 80. A California King is 72 by 84. You are trading 4 inches of width for 4 inches of length. That is the entire difference.

The name does the damage. "California King" sounds like the upgrade — the bigger, more expensive, more aspirational bed. It isn't. Run the numbers: a King is 6,080 square inches and a Cal King is 6,048. The standard King is very slightly the larger mattress, and it is meaningfully the wider one.

So the decision is not about status, it is about which axis you are short on:

• Buy a King if you share the bed and want shoulder room. Width is what makes a shared bed feel spacious, and 38 inches each is the most any standard size will give you.
• Buy a California Kingif someone in the bed is tall enough that 80 inches is genuinely short — roughly 6'2" and up — or if your room is long and narrow, where the 4 inches you give back in width buys you a walkway.

One practical warning: Cal King is the rarer size. Frames, sheets, mattress protectors and toppers all exist for it, but the selection is thinner and it is the size most likely to be out of stock in the model you want. Buy it because you need the length, not because it sounds grander.

Split king: why two Twin XLs make a King

Look at the table again. A Twin XL is 38 by 80. Two of them side by side is 76 by 80 — the exact footprint of a standard King. That is not a coincidence; it is a design decision, and it is the reason Twin XL exists as a size at all rather than being a dorm-room curiosity.

A split king is two Twin XL mattresses on one King-sized frame, and it solves two problems that a single King cannot:

• Two different firmnesses in one bed. If one of you is a 130 lb side sleeper and the other is a 220 lb back sleeper, there is no single surface that is right for both of you — the same mattress genuinely feels firmer to the lighter person. A split king lets each side be a different bed. Our firmness guide explains why that mismatch is so hard to solve any other way.
• Independent adjustable bases. One of you can sit up and read while the other lies flat. On a single King, you both go wherever the base goes.

The trade-offs are real and worth stating. There is a seam down the middle, which matters if you sleep in the centre or want to sprawl across it. And the bedding is fiddly: a split king sheet set is typically two Twin XL fitted sheets and one King top sheet, so you're shopping for a specific product rather than grabbing any King set.

The two sizes people get wrong

Full as a couples bed. The Full is also called a Double, and the name has convinced generations of people that it is built for two. At 54 inches it gives each person less room than a Twin. It is an excellent single bed for an adult who likes space, a fine guest room bed, and a compromise for two people only if the room genuinely cannot take a Queen.

Twin when they needed Twin XL.Twin and Twin XL are the same width — the XL is 5 inches longer, nothing more. For a growing teenager, a tall student, or anyone over about 5'10", those 5 inches are the whole point. Buying a Twin for someone who will outgrow it in two years is a false economy.

Once you know your size

Size is the easy decision — it is arithmetic, and the numbers above are the whole of it. What comes next is harder, because it is where the marketing lives: construction, firmness, and whether the bed will cook you.

Start with construction, because it is the biggest fork in the road and it decides how the bed sleeps more than any other spec: memory foam vs hybrid lays out the trade-off in one table. Then, when you know the size and the type you want, here are the beds worth your money: the best mattresses for the shortlist overall, or the best mattresses on Amazon if that is where you are buying — with an honest note on who each one is wrong for.