Twin XL

Twin XL keeps the twin's 38-inch width and stretches the length to 80 inches, matching a queen and a king exactly. Those 5 extra inches are the entire reason the size exists, and nothing else about it changes.

University housing standardized on it decades ago because dorm rooms are narrow and students are not short, and the size stayed. It is also half of a split king. Two Twin XL mattresses pushed together measure 76 by 80, which is a king. That pairing is how adjustable bases let two people raise their own half of the bed on their own.

Day to day it behaves like a twin with the foot problem solved. One sleeper up to about 6 foot 2 clears the end with inches to spare. The room loses nothing, since the footprint is unchanged. Two adults still do not fit: side by side they get 19 inches each, less than a full gives.

Bedding is the recurring cost. A standard twin fitted sheet is cut for 75 inches. It either will not reach the corners or pops off in the night. Twin XL sheets are also stocked far less deeply than twin or queen. Flat sheets and comforters usually cross over because nothing has to grip; check the fitted sheet and the mattress protector specifically.