Mattresses come in a standard array of sizes, with some variations in shape or composition. Twin mattresses measure 39 inches by 75 inches, full mattresses are 54 inches by 75 inches, queen mattresses are 60 inches by 80 inches and king mattresses are 78 inches by 80 inches. California king mattresses, the largest commercial standard mattresses, measure 72 inches by 84 inches. College dorms commonly have twin XL mattresses that are 5 inches longer than normal twin mattresses. Daybed and trundle mattresses are the same size as twin beds.