Buying a mattress without knowing the exact dimensions is like buying shoes without knowing your size. The names sound familiar, twin, full, queen, king, but the actual inches vary more than most people expect, and a few inches in the wrong direction can mean a bed that does not fit the room, the frame, or the sheets you already own.
This guide lists every standard US mattress size with exact measurements, explains who each size suits, and shows how to pick the right one for your room. If you are still deciding on the mattress itself, our mattress buying guide covers types and firmness, and the bed frame buying guide covers what goes underneath.
Standard US Mattress Sizes: The Complete Chart
These are the industry-standard dimensions. Individual manufacturers can vary by up to an inch, so always check the spec sheet for the exact model you are buying, but these numbers are the baseline everything is built around.
| Size | Dimensions (inches) | Dimensions (cm) | Best for |
|---|---|---|---|
| Twin | 38 x 75 | 97 x 191 | Kids, single sleepers, small rooms |
| Twin XL | 38 x 80 | 97 x 203 | Tall teens, college dorms, split kings |
| Full (Double) | 54 x 75 | 137 x 191 | Single adults who want space, guest rooms |
| Queen | 60 x 80 | 152 x 203 | Couples, most primary bedrooms |
| King | 76 x 80 | 193 x 203 | Couples who want maximum space |
| California King | 72 x 84 | 183 x 213 | Tall sleepers who need extra length |
Size by Size: Who Each One Suits
Twin (38 x 75 inches)
The standard single bed. Ideal for children’s rooms, where it leaves maximum floor space for playing, and for small guest rooms or studio apartments. An average-height adult can sleep on a twin, but at 38 inches wide there is not much room to sprawl. Bunk beds and daybeds are almost always twin size.
Twin XL (38 x 80 inches)
Five inches longer than a standard twin, which makes it the choice for taller teenagers and college dorms (dorm beds are overwhelmingly twin XL). Two twin XLs pushed together make a split king, a popular setup for couples with very different firmness preferences, since each side can be a different mattress. If you are over 6 feet tall and sleeping solo, twin XL is worth considering over a full.
Full / Double (54 x 75 inches)
Sixteen inches wider than a twin but the same length. A full works well for a single adult who likes sleeping space, and it is the classic guest-room size: comfortable for one, workable for two for a few nights. For couples sleeping on it nightly, though, 27 inches per person is tight. Most couples who try a full as their main bed upgrade to a queen within a couple of years.
Queen (60 x 80 inches)
The most popular mattress size in the US, and the default recommendation for couples. Thirty inches of width per person is enough for most couples to sleep comfortably, and the 80-inch length suits sleepers up to about 6 feet tall. Queen bedding and frames are also the easiest to find in any style and price range. If you are unsure which size to buy, buy a queen, provided your room can fit it (see the room-fit section below).
King (76 x 80 inches)
Sixteen inches wider than a queen, the same length. A king gives each partner 38 inches, the width of an entire twin bed, which is transformative if one of you is a restless sleeper, if kids or pets regularly end up in the bed, or if you just like space. The trade-offs are real: kings cost more (mattress, bedding, and frame all jump in price), they are heavy and hard to move, and they dominate smaller rooms. You also need fitted sheets specifically sized for the extra depth of modern mattresses.
California King (72 x 84 inches)
Four inches narrower and four inches longer than a standard king. The Cal king exists for tall sleepers: if you are over 6-foot-2, those extra 4 inches of length matter more than the lost width. It is less common than the standard king, so bedding choices are narrower and sometimes pricier. Unless you are tall, the standard king is usually the better pick for couples.
Will It Fit? Mattress Size vs Room Size
The mattress is only part of the footprint. Add the frame (typically 2 to 4 inches wider and longer than the mattress) and the walkway clearance you need around it: at least 24 inches on each side you use, 30 for comfort.
Minimum comfortable room sizes by mattress size (mattress plus frame plus walkways on two sides and the foot):
- Twin / Twin XL: fits comfortably in a 7 x 10 foot room
- Full: needs at least a 9 x 10 foot room
- Queen: needs at least a 10 x 10 foot room
- King: needs at least a 12 x 12 foot room
These are minimums, not ideals. A queen in a 10 x 10 room works, but there will not be space for much beyond nightstands. If your room is on the borderline, measure carefully and consider whether dropping a size would buy you a meaningfully better layout. Our small bedroom bed frame guide has more on making tight rooms work.
Thickness and Sheet Depth: The Forgotten Dimension
Mattress thickness (profile) typically runs 6 to 14 inches, and it affects more than comfort. Deep modern mattresses, especially pillow-top hybrids, need deep-pocket fitted sheets: check the sheet’s pocket depth against your mattress thickness plus any topper. A 14-inch mattress with a 2-inch topper needs sheets rated for at least 16 inches.
Thickness also changes the total bed height. Add the frame height plus the mattress: the sweet spot for getting in and out comfortably is a total sleeping surface of 22 to 26 inches off the floor. A thick mattress on a tall frame can leave shorter sleepers climbing, while a thin mattress on a platform can feel oddly low.
Specialty and Non-Standard Sizes
Beyond the six standards, a few more sizes show up often enough to know about:
- Split king (2x twin XL): two 38 x 80 mattresses side by side on one king frame. Lets couples choose different firmness levels.
- Split queen: less common, two 30 x 80 halves. Same idea on a smaller scale.
- RV / camper sizes: shorter and sometimes narrower than standards (e.g., RV queen at 60 x 75). Measure your RV bunk before ordering.
- Crib (28 x 52): the standard crib mattress size, regulated for a snug fit with no gaps.
- Olympic queen (66 x 80): 6 inches wider than a standard queen. A niche size from a few manufacturers, mostly of interest to couples who find a queen just slightly too narrow.
How to Measure for a New Mattress
Before ordering, run through this checklist:
- Measure the room: length and width, noting door swings, closet doors, and window positions.
- Measure the frame: inside dimensions where the mattress sits, not the outside. A queen frame’s mattress cavity should be about 60 x 80.
- Measure the delivery path: narrowest doorway, hallway turn, and stairwell. King and Cal king mattresses are the hardest to maneuver; many ship compressed in a box specifically to solve this.
- Check your sheets: if you own good sheets in a size, factor that into the decision. Replacing a full sheet set adds real cost.
- Confirm the exact specs: check the manufacturer’s listed dimensions for the specific model, since real products vary slightly from the nominal sizes above.
The Bottom Line
For most adults, the decision comes down to queen vs king: queen if the room is under 12 x 12 or the budget is tight, king if you have the space and share the bed. Solo sleepers are usually happiest on a full or queen, kids on a twin or twin XL, and tall sleepers should pay attention to length (twin XL, Cal king) rather than just width. Measure the room, measure the frame, measure the hallway, and then order with confidence.