What size mattress do I need?
Four questions: who's in the bed, how tall they are, how they sleep, and how much floor you have.
Short answer: couples will likely want at least a queen, couples who share the bed with a child will likely want a king, and anyone over 6 ft should look for at least 80 in of length.[1 · Oct 29, 2026] Then check that the bed leaves about 24 in of walking space around it.[1 2 · Oct 29, 2026]
1. Who shares the bed?
This is the biggest factor.[1 · Oct 29, 2026]
| Who sleeps in it | Start with | Why |
|---|---|---|
| One child or teen | Twin | Suits children and teens; affordable, and frames and bedding are easy to find.[1 · Oct 29, 2026] |
| One adult under 6 ft | Full | Roomy for one, with space to share with a pet.[1 · Oct 29, 2026] |
| One adult over 6 ft | Twin XL or queen | Both are 80 in long, as long as a king.[1 · Oct 29, 2026] |
| A couple | Queen | The most common size, so accessories are easy to find.[1 · Oct 29, 2026] Each person gets 30 in of width.[2 · Oct 29, 2026] |
| A couple plus a child at times | King | The widest standard size.[1 · Oct 29, 2026] Each adult gets 38 in.[2 · Oct 29, 2026] |
| A couple plus a pet at the foot | California king | The longest standard size; pets at the foot call for legroom.[1 · Oct 29, 2026] |
2. How tall are you?
- Under 6 ft: any standard length should give enough legroom.[1 · Oct 29, 2026]
- Over 6 ft: at least 80 in of length, so twin XL, queen, king or California king.[1 · Oct 29, 2026]
- Over about 6′2″: 80 in starts to run short; the 84 in California king is the standard size with more length.[2 · Oct 29, 2026] Another guide puts that point at about 6′4″.[3 · Oct 29, 2026]
3. How do you sleep?
Back and stomach sleepers lie fully stretched out, so legroom matters more for them than for side sleepers.[1 · Oct 29, 2026] On a queen, each of two sleepers gets 30 in of width, which is 8 in narrower than a twin; two restless sleepers who wake each other may be happier on a king.[2 · Oct 29, 2026]
4. Will it fit the room?
Leave about 24 in around each side of the bed.[1 · Oct 29, 2026] One maker's minimum room sizes: 7′ × 10′ for a twin, 9′ × 10′ for a full, 10′ × 10′ for a queen and 12′ × 12′ for a king or California king.[2 · Oct 29, 2026] A frame and headboard can add up to 5 in each way.[2 · Oct 29, 2026] Details on our room size page.
Think ahead
Buying for a small child? Consider one size up so they don't outgrow it. Buying your first bed as a single adult? A bigger size leaves room for a future partner or pet.[1 · Oct 29, 2026] Less common sizes, especially California king and twin XL, have pricier sheets, blankets and frames.[1 · Oct 29, 2026]
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Sources: 1. Sleep Foundation, Mattress sizes and dimensions guide. 2. Casper, Queen size bed dimensions: size, room fit, and how it compares. 3. Sleep Foundation, Queen vs. king. Checked Oct 29, 2026. Trademarks belong to their owners; figures are restated in our own words and tables, not reproduced.