Convert Mattress Sizes (King, Queen & More)
King is 76 × 80 in (193 × 203 cm); Queen is 60 × 80 in (152 × 203 cm). US Full is not identical to UK Double—compare footprints, then check room fit.
Mattress size cheat sheet
King, Queen, Full, and Twin footprints are below—inches and cm match the chart rows. US Full is often called Double; UK Double is a different size.
How to choose a mattress size (quick)
- Room: Leave about 2–3 feet to walk on the sides you use.
- Sleepers: One person → Twin or Full; two → Queen or King.
- Length: Tall sleepers often prefer Twin XL, Queen/King length (80 in), or California King (84 in).
- Region: UK Double ≠ US Full—match cm before you order sheets.
Mattress size FAQ
Crib, topper & special sizes
Crib: Standard crib mattress is 27.25 × 51.625 in (69.2 × 131.1 cm) (ASTM F1425). Never cut down an adult mattress for a crib.
Toppers / protectors: Match the size label to your mattress (King topper → King mattress). Thickness is a comfort choice, not a footprint.
RV: RV Queen / King are often shorter than home sizes—check the converter’s special sizes before you order.
Data sources
- Standard mattress sizes: ISPA (International Sleep Products Association)
- RV mattress sizes: RV Industry Association
- Crib mattress sizes: ASTM F1425
- Last updated: September 8, 2026
Related tools & guides
Mattress size chart
King, Queen, Full, Twin, Cal King, crib, and UK sizes in one table.
How to choose mattress size
Room, sleepers, and when to size up to King.
Mattress size comparison
Twin vs Full vs Queen vs King side by side.
Foam vs hybrid (coil)
Construction differences after you lock the size.
Bed sheet size chart
Sheets matched to mattress footprints.
Pillow size chart
Standard, Queen, King, and Euro pillows.