A standard twin mattress is typically 75 inches long (about 6 feet 3 inches) and 38 inches wide. This size is the smallest standard mattress size and is well suited for children, teenagers, and adults under 6 feet tall

. There is also a twin XL mattress, which is 5 inches longer, measuring 80 inches in length while maintaining the same width of 38 inches. The twin XL is often chosen by taller individuals or for college dorm rooms

. In summary:

• Twin mattress: 38 inches wide by 75 inches long
• Twin XL mattress: 38 inches wide by 80 inches long

The standard twin mattress length is 75 inches