Bed size is directly related to corresponding mattress size. The standard mattress sizes are twin (39 by 74 inches), twin XL (39 by 80 inches), full (54 by 74 inches), queen (60 by 80 inches), king (76 by 80 inches) and California king (72 by 84 inches).
Another less common mattress size is crib size which is typically 27 by 51.5 inches. Mattress dimensions can vary by product and manufacturer, although variations are usually within half an inch of the standard measurements. Twin, twin XL and full size mattresses are suitable for one person, and queen, king, and California King size mattresses are suitable for two people.