There are nine mattress sizes available, according to the Better Sleep Council. In addition to the standard twin, twin extra-long, full, queen, king and California king mattress sizes, there are also special mattresses for futons, cribs and toddler beds.
A twin-size mattress is 38-inches wide by 75-inches long, says the Better Sleep Council. This is the smallest mattress size available beyond a crib-size mattress. A twin XL mattress is also about 38-inches wide, but it is several inches longer. The twin XL is recommended for small spaces, and it is often used in college dorm rooms.
A full mattress, also called a double, measures 53-inches wide by 75-inches long. Both the regular twin and a full may be too short for people over 5 feet 5 inches tall, cautions the Better Sleep Council.
A queen mattress is 60-inches wide by 80-inches long. A king-size mattress is considerably wider than a queen, measuring approximately 76-inches wide by 80-inches long. It is roughly the same size as two twin XL mattresses laid side by side, claims the Better Sleep Council. A California king measures 72-inches wide by 84-inches long, or 4 inches narrower and 4 inches longer than a typical king-size mattress.