Two adults fit on a full-sized bed, states The Bedding Experts. Couples once commonly slept on full-sized beds, but as of 2015, most couples opt for a queen-sized bed. A full-sized bed is ideal for a child, teenager or shorter adult, says Better Sleep Council.
A full mattress is 54 inches wide and 75 inches long, notes The Bedding Experts. If two people sleep on a full mattress, each has 27 inches of sleep space, which is equivalent to the sleep space on a crib mattress. A queen mattress is 60 inches wide and 80 inches long, providing each occupant with a sleep space that is 3 inches wider and 5 inches longer than that of a full mattress.