The Twin Extra Long size of bedding is often called "twin XL" and is not commonly used in homes. However, it is very common in dorm rooms at U.S. universities as it is as wide as a twin bed but longer to accommodate taller students. It is 39 inches wide by 80 inches long, about 5 inches longer than a regular twin size. Two twin XL mattresses can be put together to form one king size bed.
Sheets for twin XL beds are 39 by 80 inches long. However, only fitted (or box) sheets are made to fit the mattress. Top sheets and comforters are generally not made in twin XL size, so purchase twin or full sizes according to your needs. Retailers that specialize in dorm bedding often sell twin XL size mattress pads or "egg carton" foam to make the beds more comfortable. Dorm beds are generally quite firm from years of use.
Some college dorm rooms will have bunk beds to save space. Bunk beds for use in dormitory situations generally come as two twin XL beds or sometimes a twin XL as one bed and a full size bed as the other. A full size bed is 54 by 75 inches. Find out what kind of bed will be in your dorm room and verify its size before buying bedding, and also decide if you feel you will need guard rails if you are on the top bunk.
Loft beds consist of the top portion of the bunk bed with an open space or storage underneath. This type of bed is a popular option to save space in small dorm rooms. An existing bed in a dorm room can be made into a loft using wood or kits designed for this purpose. However, check with the university first to make sure it is OK to build the loft bed as many universities are worried about liability if the bed breaks.