Twin Size Mattress Dimensions
Quick answer: a Twin size mattress is 38 inches wide × 75 inches long — 97 × 191 cm, or 3.2 × 6.3 feet. It is the smallest standard adult mattress size, made for one sleeper, and the most common choice for children’s rooms, bunk beds and small guest rooms.
Short answer: The standard twin mattress size is 38 inches wide × 75 inches long (97 × 191 cm, 3.2 × 6.3 ft). It sleeps one person, fits a room as small as about 7 × 10 ft, and is the default size for kids’ beds, bunks and trundles. Sleepers approaching 6 ft tall should choose the 80-inch Twin XL instead.
Twin Mattress Dimensions Chart
| Measurement | Inches | Centimeters | Feet |
|---|---|---|---|
| Width | 38″ | 97 cm | 3.2 ft |
| Length | 75″ | 191 cm | 6.3 ft |
| Surface area | 2,850 sq in | 1.84 m² | 19.8 sq ft |
A Twin frame’s inside dimensions should be at least 38″ × 75″; with rails and a headboard most Twin frames measure about 41–43 inches wide overall. Two Twins side by side equal the width of a King — which is why two Twin XLs are used for Split King beds (see below).
These are the same standard dimensions listed in the Sleep Foundation’s mattress sizes guide, which also explains why each single size suits best.
Twin vs Twin XL
| Twin | Twin XL | |
|---|---|---|
| Dimensions | 38″ × 75″ | 38″ × 80″ |
| Best for | Kids, bunk beds | Tall teens, dorms, Split King |
| Bedding | Twin sheets | Twin XL sheets (longer) |
The only difference is 5 inches of length — but for anyone approaching 6 feet tall, those 5 inches decide whether their feet hang off the end. Full details are on our Twin XL mattress size page, and every size is compared in the mattress sizes chart.
The Sleep Foundation’s Twin XL vs Full comparison makes the same point from the buyer’s side: length decides for tall sleepers, width decides for everyone else.
Twin Mattresses for Bunk Beds, Trundles and Daybeds
Three of the most common Twin setups use the same 38″ × 75″ footprint but different rules. Bunk beds are almost always Twin on top and bottom, and the top bunk adds a thickness limit: the guard rail must extend at least 5 inches above the mattress surface, so most bunk makers cap the mattress at 6″–8″ thick — check the stamp on the frame before ordering a plush model. Trundles (the pull-out bed under a main bed) are Twin width and length but shallower still, usually 6″ thick at most, because the closed trundle must clear the frame above it. Daybeds take a standard Twin with no special limits, which is why they double so well as guest beds and sofa seating. In all three cases the sheets are ordinary Twin sheets; only the thickness changes.
For a toddler who is not yet ready for a full Twin room yet, the in-between step is a mini crib: see the mini crib mattress size guide for its 24″ × 38″ footprint.
Who Should Buy a Twin?
The twin mattress size works best for one sleeper in a smaller room. These are the classic cases:
- Children and younger teens — the standard step up from a crib or toddler bed.
- Bunk beds and trundles — almost always Twin size (check thickness limits for guard rails).
- Small rooms and studio apartments — a Twin fits a room as small as 7 × 10 ft.
- Guest rooms — two Twins give flexible sleeping for kids or single guests.
Most children arrive at a Twin straight from the nursery — our crib mattress size guide covers the bed they are leaving, including when the move should happen.
Adults of average height can sleep on a Twin, but most find it narrow for every night. If the sleeper is over 5 ft 10 in, go straight to the Twin XL.
When a teen outgrows the Twin’s width rather than its length, the natural upgrade is a Full size mattress (54″ × 75″) — same length, 16 inches wider.
What Is the Minimum Room Size for a Twin Bed?
A Twin is the easiest size to place: the mattress needs a floor footprint of just 38″ × 75″, and with a typical frame (about 41″ × 78″ overall) a room of 7 × 10 ft still leaves a workable 24-inch walkway on one side and at the foot. In a 7 × 9 ft room it fits along the long wall with the walkway reduced to the foot end only — fine for a child’s room with a small dresser, tight for an adult’s full-time bedroom. Two Twins in one shared kids’ room need roughly 10 × 10 ft to keep a gap between beds and room for a shared desk.
Choosing between a Twin, a Twin XL and a Full for the same room? The three-question mattress size finder settles it in under a minute.
Related Mattress Size Guides
- Twin XL Mattress Size — 38″ × 80″, the longer single
- Full Size Mattress Dimensions — the wider upgrade
- Crib Mattress Size — the bed before the Twin
- Mattress Size Guide & Finder — pick a size in three questions
Frequently Asked Questions
What are the exact dimensions of a twin mattress?
The twin mattress size is 38 inches wide by 75 inches long (97 × 191 cm, or 3.2 × 6.3 feet).
Can an adult sleep on a twin bed?
Yes, but it is snug. Adults under about 5 ft 10 in manage fine; taller adults should choose a Twin XL.
Do two twin mattresses make a king?
Two Twin XL mattresses (38″ × 80″ each) make a Split King. Two regular Twins make a bed 76″ × 75″ — King width but 5 inches shorter than a true King.
What size sheets fit a twin mattress?
Twin sheets are cut for 38″ × 75″. Twin XL sheets will bunch on a regular Twin because they are 5 inches longer.
Is a twin the same as a single?
Yes — in the US, “single” and “Twin” refer to the same 38″ × 75″ size.
Sources: Sleep Foundation — Mattress Sizes guide; Sleep Foundation — Twin XL vs Full.