This bed is gorgeous! We got a twin size, and even though some of the other reviewers said a XL twin mattress was needed, we found out that is not the case. A XL mattress will be 80". The measurement from the OUTSIDE of the headboard to the OUTSIDE of the footboard is 80"; however, measuring from the INSIDE of the headboard to the INSIDE of the footboard (which is actually where the mattress will be) is 78.5". Therefore, a regular twin size mattress is needed.