Ad Up to 70 Off On Mattress and Beds Huge Range Fast Delivery. This is a good. Dorm Room Bedding Sizes 101 Learn About Bedding For Your Dorm Room And The Difference Between Twin And Twin Extra Long Be Mattress Pad Mattress Mattress Guide The dimensions of a Cal King mattress are 72 wide by 84 long. How much longer is a twin xl . Though it is not a common practice parents do purchase twin XL mattresses for their children to accommodate their. A twin XL size mattress is 38 inches wide by 80 inches long Same Width Different Lengths Both the standard twin and twin extra long XL size mattresses are 316 feet in width but a twin XL is longer. If two twin XL mattresses were put next to each other the total dimensions would be 76 wide by 80 long. There is no difference in the width measurement 38 inches sometimes 39 inches so both bed sizes are only suited for single sleepers and are not recommended for couples. It adds 6 inches to the height of the standard twin. The twin XL has t...