Buy EcoBox 80 x 8 x 79 Inches Shipping/Moving Carton for Queen or King Size Mattress/Box Spring (E-2411): Mattress Encasements – Amazon.com FREE DELIVERY possible on eligible purchases Buying a too-small mattress is one of the biggest mistakes new bed-buyers make. Couples who’ve been sleeping on a “double” (also known as a full-size mattress) since they got together may think they have enough room – until they learn that each person has only as much sleeping space as a baby’s crib! Standard bed sizes are based on standard mattress sizes, which vary from country to country.Bed sizes also vary according to the size and degree of ornamentation of the bed frame.Dimensions and names vary considerably around the world, with most countries having their own standards and terminology. In addition, two mattresses with the same nominal size may still have slightly different Twin XL The twin’s slightly longer cousin, the twin XL mattress is the most popular size for college dorm rooms. It’s five inches longer than a twin, making it 39 inches wide and 80 inches long. In addition to students, a twin XL mattress is a good solution for taller teenagers and individual adults with limited space. .