What are the dimensions of a twin-size mattress in length and width?

A twin-size mattress is 39 inches wide and 75 inches long. The depth of a twin mattress can be between 9 and 16 inches, as there is no standard depth for a mattress.

Mattresses can be made with inner springs, which are metal coils ranked from 12 to 18; 12 is the thickest coil, and 18 is the thinnest. Mattresses can also be made of memory foam or latex, or they can be filled with air.

Twin beds are often used for a single adult or a child who has outgrown a crib. Twin-size mattresses are best for daybeds and beds that can be hidden away.