Didn't find what you were looking for?  Visit our Ecommerce site at www.thekidsroomfurniture.com to see an even larger selection of furniture! Twin Beds Twin beds are the traditional size for children.  The mattress for a twin measures approximately 38 inches wide by 74 inches long. All of our twin beds accept a standard twin mattress.  You'll find a wide range of styles, finishes, and materials in this size bed.