Measured: US standard sizes are quoted width by length in inches, measured across the mattress itself rather than the frame around it.
The basics
What to know about bed size
Bed size fixes three purchases at once: the mattress, the base or frame under it, and every sheet, protector and duvet you buy afterward. Name it right and the rest of the bedroom follows. Name it wrong and a fitted sheet fights you every wash.
Sizes are named, not measured, so read the inches. US mattresses are quoted width first and length second, and the six standard cuts run from 38 inches wide to 76. Width divides between sleepers. Length answers height. A workable rule is to add 6 inches to the taller sleeper's height. A 6-foot person needs 78 inches and fits an 80-inch bed, while a 6-foot-4 person does not.
Read the six in two blocks. Twin, Twin XL and Full are single-sleeper sizes, with Full offering room to sprawl rather than room to share. Queen, King and California King are couple sizes, and the step from Queen to King buys 16 inches of width, the largest single comfort jump on the chart. Measure the room before the mattress, and leave at least 24 inches of clear floor on every side you need to walk. Check the doorway and the stair turn too. A mattress that will not reach the bedroom is the wrong size whatever the label says.
