In the United States there are six standard mattress sizes: Twin (38″ × 75″), Twin XL (38″ × 80″), Full/Double (54″ × 75″), Queen (60″ × 80″), King (76″ × 80″) and California King (72″ × 84″). A king is the widest standard size at 76 inches; a California King is four inches narrower but four inches longer. Use the chart below to compare every size in inches and centimetres, then check the room-fit and bedding notes before you buy.
Standard bed size chart (inches and centimetres)
These are the dimensions the mattress industry uses for standard sizes. Expect small differences of up to about an inch between brands and models, so always confirm the exact specs on the product page before ordering a frame or fitted sheets.
| Size |
Dimensions (inches) |
Dimensions (cm) |
Best for |
| Crib (full-size) |
At least 27¼ × 51⅝ |
69 × 131 |
Infants and toddlers |
| Twin (Single) |
38 × 75 |
96.5 × 190.5 |
Children, bunk beds, small rooms |
| Twin XL |
38 × 80 |
96.5 × 203 |
Tall teens, dorms, split-king halves |
| Full (Double) |
54 × 75 |
137 × 190.5 |
Solo adults, guest rooms |
| Queen |
60 × 80 |
152 × 203 |
Most couples, standard primary bedrooms |
| Olympic Queen |
66 × 80 |
168 × 203 |
Extra width without a king footprint |
| King (Eastern King) |
76 × 80 |
193 × 203 |
Couples who want maximum width |
| California King |
72 × 84 |
183 × 213 |
Tall sleepers, long narrow rooms |
| Wyoming King |
84 × 84 |
213 × 213 |
Oversized square bed, co-sleeping |
| Texas King |
80 × 98 |
203 × 249 |
Very tall sleepers, large rooms |
| Alaskan King |
108 × 108 |
274 × 274 |
Maximum space, whole-family sleeping |
The crib figure is a safety requirement rather than a marketing size: under the federal crib mattress standard, a full-size crib mattress must measure at least 27¼ inches wide and 51⅝ inches long so there is no dangerous gap at the sides (CPSC final rule, Federal Register). Crib mattress thickness is also capped at six inches.
How much room does each bed size need?
Mattress dimensions only tell half the story. Interior designers commonly suggest leaving roughly 24 to 30 inches of clear walkway on the sides you actually use, plus room for nightstands, drawers and door swings. These room sizes are practical rules of thumb, not standards — a slightly smaller room can still work if the bed sits against the long wall and only one side is used as a walkway.
| Mattress |
Comfortable room size (rule of thumb) |
Notes |
| Twin |
About 7′ × 10′ |
Leaves space for a desk or dresser |
| Twin XL |
About 8′ × 10′ |
Same width as Twin, five inches longer |
| Full |
About 9′ × 10′ |
One nightstand fits more easily than two |
| Queen |
About 10′ × 10′ |
Fits most standard bedrooms with two nightstands |
| King |
About 12′ × 12′ |
Roughly two feet of clearance per side |
| California King |
About 12′ × 14′ |
Extra length eats into foot-of-bed space |
| Oversized (Wyoming, Texas, Alaskan) |
14′ × 14′ or larger |
Check doorways, stairs and delivery path first |
Remember that the frame adds to the footprint. Platform, storage and upholstered beds typically add a couple of inches on each side, and a headboard adds several inches of length — see our guide to choosing a bed frame for your mattress and style if you are shopping for both at once.
What size is a king mattress?
A standard king (sometimes called an Eastern King) is 76 inches wide by 80 inches long — 193 × 203 cm. It is the same length as a queen but 16 inches wider, which works out to about 38 inches of width per person for a couple: the same width each sleeper would get on a Twin XL. That is also why two Twin XL mattresses side by side add up to a king footprint and form the basis of split-king setups.
A king is the best standard choice if you want maximum elbow room, share the bed with children in the morning, or sleep with a pet at your side. The trade-offs are a larger room requirement, heavier mattresses that are harder to move up stairs, and higher costs for sheets, duvets and frames. For a full breakdown of clearances, frame sizes and layout tips, see our king size mattress dimensions guide.
King vs California King
Choose width or length — you cannot have both in a standard size. A King is wider, a California King is longer.
- King — 76″ × 80″: four inches wider per couple, better for side-by-side space, easiest of the two to find bedding for.
- California King — 72″ × 84″: four inches longer, which suits sleepers around 6’2″ and taller, and fits long, narrow rooms more gracefully.
If you are torn between the two, our King vs California King comparison walks through frame sizes and room layouts for each.
The best bed size for couples
For two adults, a Queen is the usual starting point and a King is the upgrade. The simple maths helps: a Full gives each person about 27 inches of width, a Queen 30 inches, and a King 38 inches. Queen has long been the most-purchased size in the US — survey data put it at roughly half of mattress purchases (Statista), largely because it fits a typical 10′ × 10′ bedroom while still sleeping two.
| Size |
Width per sleeper |
Who it suits |
| Full |
27″ |
Short-term or small-room solution for two; tight for most couples |
| Queen |
30″ |
Most couples in average bedrooms; widest bedding selection |
| King |
38″ |
Restless sleepers, co-sleeping with kids or pets |
| California King |
36″ |
Couples where one partner is very tall |
| Split King (two Twin XL) |
38″ |
Partners who want different firmness or adjustable bases |
Does a bigger bed actually improve sleep? The direct evidence is thin — there is no large study comparing queens with kings. Research on bed sharing does show that couples move more and wake more often when sleeping together than alone, even though they tend to rate their sleep as better, and one polysomnography study found bed sharing was associated with more and more stable REM sleep (Frontiers in Psychiatry). Extra width is a reasonable response to that extra movement, but so is a mattress with good motion isolation and separate blankets. If you want to go deeper on the comfort side, see our guide to bed size and sleep quality.
Sizes for kids, teens and guest rooms
- Twin (38″ × 75″): the default for children’s rooms, bunk beds and daybeds. Too short for most adults over about six feet.
- Twin XL (38″ × 80″): the same width with five extra inches of length, standard in many college dorms, and a size a growing teen will not outgrow.
- Full (54″ × 75″): a good single-sleeper upgrade and the most space-efficient choice for a guest room that sees occasional couples. See our full size bed dimensions guide for layout ideas.
- Queen (60″ × 80″): the most flexible guest-room size if the room can take it, and the easiest to dress with off-the-shelf bedding. Details in our queen size bed dimensions guide.
Split, oversized and custom sizes
Beyond the standards, a handful of specialty sizes solve specific problems. All of them come with the same caveats: fewer frame options, longer lead times and bedding that may have to be ordered to size.
| Size |
Dimensions |
Why choose it |
| Split King |
Two mattresses, 38″ × 80″ each |
Independent firmness and adjustable-base positions |
| Split California King |
Two mattresses, 36″ × 84″ each |
Same benefits with extra length |
| Olympic Queen |
66″ × 80″ |
Six inches more width than a Queen; a specialty size, so bedding is limited |
| Wyoming King |
84″ × 84″ |
Square bed with king-plus width, Cal King length |
| Texas King |
80″ × 98″ |
The longest of the oversized options |
| Alaskan King |
108″ × 108″ |
Nine-foot square for families sleeping together |
Fully custom mattresses are also available for lofts, RVs, boat cabins and rooms with angled walls, usually in custom widths and lengths and occasionally in round or cut-to-fit shapes. Before committing, confirm three things: that a frame or foundation exists in that size, that you can buy sheets and a duvet for it, and that the mattress will physically make it through your doorways and stairwell.
How to measure your room before you buy
- Measure wall to wall — length, width and ceiling height if you want a tall headboard.
- Mark the obstacles — doors, closet and drawer swings, radiators, windows and outlets.
- Tape the footprint — outline the mattress plus two to six inches for the frame with painter’s tape and live with it for a day.
- Walk the walkways — you want about 24 to 30 inches on the sides you use, and enough space at the foot to pass or open a drawer.
- Check the delivery path — hallway width, stair turns and door frames. Split configurations and mattresses in a box solve most access problems.
Bedding fit: the detail most charts leave out
Length and width determine your sheet size, but mattress height determines whether a fitted sheet stays on. Modern mattresses vary widely in depth, and a pillow-top plus a topper can easily exceed a standard sheet pocket — check the pocket depth listed on the packaging against your mattress height plus any topper. A few more practical notes:
- Queen and King have the widest choice of sheets, duvets, protectors and frames; California King and specialty sizes have fewer options and often cost more.
- Split setups need either two Twin XL sheet sets or purpose-made split-top sheets.
- Duvet sizing is generous by design — many people size up one step so the cover drapes over the sides of a taller mattress.
Common bed-size mistakes
- Measuring the mattress but not the walkway. A king can technically fit a 10′ × 10′ room and still make the room unusable.
- Choosing width when you need length. If your feet hang off an 80-inch mattress, a California King or Twin XL solves the problem that a wider bed will not.
- Forgetting the frame and headboard. Add two to six inches in each direction to the mattress footprint.
- Ignoring bedding availability. Specialty and oversized sizes can mean custom-order sheets for the life of the bed.
- Buying for today only. A mattress is typically a several-year purchase; factor in growing children, pets and future guests.
- Skipping the trial policy. Comfort and support are hard to judge in a showroom, so read the return and trial terms before ordering. Consumer Reports’ mattress buying guide is a useful neutral starting point for types and firmness.
FAQ
What are the dimensions of a king size mattress?
76 inches wide by 80 inches long (193 × 203 cm). That is 16 inches wider than a queen and the same length.
How wide is a king size mattress compared with a California King?
A king is 76 inches wide; a California King is 72 inches wide but 84 inches long. King wins on width, Cal King on length.
What is the most popular bed size?
The Queen (60″ × 80″). Survey data has put it at close to half of US mattress purchases, thanks to its balance of sleeping space, room fit and bedding availability.
Is a Full big enough for two people?
It can work short term, but each person gets only about 27 inches of width — narrower than a crib mattress. Most couples are more comfortable on a Queen or larger.
Will a king fit in a 12′ × 12′ room?
Yes. A 76-inch-wide bed leaves roughly two feet of clearance on each side, which is workable, though you will need to plan nightstands and dressers carefully.
Do mattress sizes vary by country?
Yes. UK, European and Australian sizes use different dimensions and naming, so check local specifications if you are buying or moving abroad — bedding bought overseas often will not fit a US mattress.
Do mattress dimensions vary between brands?
Slightly. Standard sizes are consistent within about an inch, but always read the listed dimensions before ordering a frame, headboard or fitted sheets.
Once you have settled on a size, the next decisions are construction and firmness. Our guide to the mattress firmness scale explains how plush-to-firm ratings translate to real support.
Updated September 2026.
