The twin bed - also called the single bed - is a popular mattress size for children, teens, and single adults alike. It's an inexpensive space saver that provides no more sleeping space than an average-height single sleeper needs.

The twin size mattress dimensions are 38" x 75", or 3.16 ft x 6.25 ft. As the smallest standard size, it's an optimal fit for childrens' rooms - in fact, the name "twin bed" comes from the idea of two children sharing a room with one twin bed each. Twin beds are a great step up when a toddler becomes too big for their crib mattress, and they're commonly used in bunk beds.

Twin beds can also be used by single adults, typically those under 5'5". (If you're over 5'5" but still want the slim width of a twin, you may want to consider a twin XL mattress - XL standing for extra long - which adds 5" of extra length to a regular twin.) In addition to height, if you're considering this bed size, make sure you're not the type of person who rolls around or sprawls out in bed. If you are, consider the full size bed or queen size bed: they will feel less cramped. 

They can even be used by couples: though the twin XL bed is more typically used to create a split king, you can also push two twin beds together. The result will be 5" shorter than a standard king, but it can work out for shorter couples. 

The twin bed is a great space-saver for people living in small apartments, college dorm rooms, or other places with small bedrooms, requiring only a 7 ft x 10 ft bedroom space. That includes the twin bed and relevant furniture, like a nightstand and a dresser.

Of all mattress sizes, the twin is the easiest to bring into your house: unlike trying to maneuver a larger mattress, like a California king, through your hallways, a twin mattress is easily carried around and moved. Everything about the twin bed is easier to move around: the bed frame is easier to carry, the bedding is more convenient to wash,

It's also an economical option: as it's about half the size of a king bed, it also typically costs about half as much. This makes it an especially good choice for furnishing dorms and guest rooms, or any place where budget is a constraint.