Question: what is the difference in size between a crib mattress and a twin mattress?
Answer: 38″ x 75″ A twin (or “single”) mattress is the smallest possible mattress size other than a crib-size mattress. Twin mattress dimensions are approximately 38 inches wide by 75 inches long. ... A twin mattress is a good choice for children who have outgrown their cribs (see Crib Ideas).