The most popular question new college students and their parents have this time a year is just exactly how long is a twin XL size bed? Twin XL stands for Twin Extra Long not extra large. Twin XL beds are 5 inches longer than a normal Twin size bed, measuring a total of 80 inches in length. Twin XL mattresses are the same width as normal Twin size mattresses at 39 inches wide. Where to Buy Twin XL Sheets? TwinXL.com is the Twin XL Superstore! Carrying the finest collection of twin XL bedding and accessories. Match a wide variety of color schemes and patterns with the largest selection in dorm bedding. Click here to shop Twin XL bedding .