Twin XL mattresses are slightly longer than standard twins, measuring 38 inches wide by 80 inches long. This added length makes them a great option for taller teenagers, college students, or adults who need a bit more legroom but don’t have the space for a wider bed. Twin XLs are the standard in most college dorms and can also be used in adjustable bed bases. Two Twin XLs can be combined to create a split king setup for customizable comfort.