A twin mattress is 75 inches long and 38 inches wide. In feet that is 6 feet 3 inches by 3 feet 2 inches, and in metric it is roughly 191 by 97 centimeters.
That length is the number most people are actually checking, usually for one of three reasons: they are buying a bed frame, they are working out whether a tall teenager will still fit next year, or they are trying to figure out why the twin sheets they bought do not fit the dorm bed. All three come down to the same 75 inch figure and what it does not cover.
Twin mattress dimensions
| Measurement | Value |
|---|---|
| Length | 75 inches (6 ft 3 in / 191 cm) |
| Width | 38 inches (3 ft 2 in / 97 cm) |
| Height (profile) | Typically 8 to 14 inches, varies by model |
| Sleeping surface | 2,850 square inches |
| Smallest comfortable room | Around 7 by 10 feet |
| Also called | Single |
A note on the width: you will occasionally see a twin listed as 39 inches rather than 38. Both numbers are in circulation, the difference is within normal manufacturing tolerance, and it makes no practical difference to bedding or frames. Length is standardized at 75 inches and does not vary.
Twin vs twin XL: the five inches that matter
| Size | Width | Length | Typical use |
|---|---|---|---|
| Twin | 38 in | 75 in | Kids, bunk beds, daybeds, guest rooms |
| Twin XL | 38 in | 80 in | Tall sleepers, college dorms, split king halves |
The width is identical. The only difference is 5 inches of length, and that is enough to change who the bed works for. As a rough rule, a sleeper taller than about 5 feet 10 inches will start to feel the end of a twin, and anyone at 6 feet or above will have their feet over the edge once a pillow is accounted for.
Two practical consequences people run into constantly:
- Dorm beds are almost always twin XL. Standard twin sheets will not stay on one. If you are shopping for a college move-in, buy twin XL bedding, not twin.
- Split king adjustable beds use two twin XL mattresses. Two regular twins side by side do not equal a king in either dimension, so this is not a substitution you can make.
Our twin vs twin XL comparison and our twin XL size guide go into more detail, and you can browse twin mattresses or twin XL options directly.
How a twin compares to the other sizes
| Size | Dimensions | Difference from a twin |
|---|---|---|
| Twin | 38 x 75 in | Reference size |
| Twin XL | 38 x 80 in | Same width, 5 inches longer |
| Full / Double | 54 x 75 in | 16 inches wider, same length |
| Queen | 60 x 80 in | 22 inches wider, 5 inches longer |
| King | 76 x 80 in | 38 inches wider, 5 inches longer |
Worth noticing: a twin and a full are the same length. Stepping up from a twin to a full gets you width and nothing else. If length is your problem, the smallest fix is a twin XL, not a full.
Bunk beds, daybeds and trundles
Twin is the default size for all three, which is why it remains one of the most-sold mattress sizes in the country despite being the smallest.
For bunk beds, length is rarely the issue. Thickness is. Most bunk frames have a guardrail height that assumes a mattress no more than about 6 to 8 inches thick, and a thicker mattress raises the sleeper above the rail, which defeats the point of the rail. Check your frame's stated maximum mattress thickness before you buy, not after. Our guides to bunk bed mattresses and bunk bed safety cover the clearances.
For daybeds, a twin is the standard fit and a lower profile mattress usually looks better, since a thick mattress sits above the side rails and undermines the sofa look. See what a daybed is.
For trundles, the pull-out unit takes a twin, and clearance under the main bed is the constraint. Many trundles cap out around 6 to 8 inches of mattress thickness. More on that in what a trundle bed is.
Who a twin actually fits
It works well for: children moving up from a toddler bed, teenagers under about 5 feet 10 inches, single adults in genuinely small rooms, guest rooms with occasional use, and any bunk, daybed or trundle setup.
It does not work for: anyone 6 feet or taller as a nightly bed, two people under any circumstances, or a restless sleeper who needs room to move. At 38 inches wide, a twin gives one adult less width than each person gets on a shared full, which tells you how narrow it is.
One thing worth planning for if you are buying for a child: a twin usually carries a kid comfortably from about age three into the mid-teens, and then the length becomes the problem before the width does. If the child is already tall for their age, buying a twin XL now often saves buying twice. Our guide on choosing a mattress for kids or teens works through the timing.
What to look for beyond the size
Every twin is the same size, so the decision is entirely about construction and feel.
- Firmness. Lighter sleepers, which most twin sleepers are, need less firmness than a marketing chart suggests. A medium usually suits a child or teen better than a firm.
- Profile. Measure your frame's clearance first if it is a bunk, trundle or storage bed. A 12 inch mattress that does not fit is a return.
- Construction. Memory foam is quiet and light, which matters on a bunk. Hybrids breathe better, which matters in a Los Angeles bedroom in August, especially in an older building without air conditioning.
- Durability. A kid's mattress gets jumped on. Foam density and coil gauge are what determine whether it survives that, and neither is printed on the tag, so ask.
Frequently asked questions
How long is a twin mattress?
75 inches, which is 6 feet 3 inches or about 191 centimeters. This is the same length as a full mattress. A twin XL is 80 inches long.
How wide is a twin mattress?
38 inches, which is about 97 centimeters. Some manufacturers list 39 inches, and the difference is not meaningful for bedding or frames.
What size is a twin mattress in centimeters?
Roughly 97 by 191 centimeters. A UK single is 90 by 190 centimeters, so it is slightly narrower and slightly shorter than a US twin. Fitted sheets are not reliably interchangeable between the two.
Is a twin the same as a single?
In the United States, yes. Twin and single are two names for the same 38 by 75 inch mattress. In the UK a single is 90 by 190 centimeters, which is close but not identical.
How big is a twin mattress compared to a full?
A full is 16 inches wider at 54 inches, and exactly the same length at 75 inches. So a full solves a width problem and does nothing about a length problem.
Can an adult sleep on a twin mattress?
A single adult under about 5 feet 10 inches can sleep on a twin comfortably, particularly in a small room where the footprint matters more than the sprawl. Taller adults and restless sleepers will want a twin XL or a full.
How much does a twin mattress weigh?
Usually between 40 and 65 pounds, depending on construction. All-foam twins sit at the lighter end and coil hybrids at the heavier end. Either is manageable for one person to rotate.
What size room do you need for a twin bed?
A twin fits in a room as small as about 7 by 10 feet with enough clearance to walk around one side. For a bunk bed, the more important measurement is vertical: allow at least 2 feet between the top mattress surface and the ceiling.
Do twin sheets fit a twin XL?
No. The widths match but a twin XL is 5 inches longer, so a twin fitted sheet will pull off the corners. Buy sheets labeled twin XL for dorm beds and split king halves.
Come see the sizes side by side
Five inches of length is hard to picture and easy to get wrong, especially for a child who is still growing. Come compare a twin against a twin XL in person at any of our five Los Angeles showrooms, and bring your frame measurements if it is going into a bunk or a trundle. Take our sleep quiz first if you want a starting point on firmness, or browse twin mattresses and full size mattresses online. Same-day delivery is available across most of the metro area, and every mattress comes with our free 120-night comfort guarantee.
