The standard sizes of bed frames are twin (39" x 75"), full (54" x 75"), queen (60" x 80") and king (76"x 80"). Although it is uncommon, it is also possible to find beds in an extra-large twin size, which measure 39" x 80".
These are standard American bed sizes and may differ from other international bed frame or mattress sizes. The measurements refer to the mattress frame, as the sizes of head and foot boards and other frame features differ among designs. Additionally, many companies offer custom bed frame and mattress sizes that can be made to order and do not fit into any of the previously mentioned categories.
Bed size standardization in the United States began around 1870, when dimensions for twin- and full-size beds were determined. King- and queen-size standardization followed in the 1950s.
Bed frame size dimensions can be used to determine what size is appropriate for a particular space. These dimensions may also be used in comparison with box spring size to determine an appropriate mattress size.