Toddler beds use the same mattress as the crib and are generally low to the ground with side rails. This is a transitional bed that offers some of the features of a crib, such as the side rails to keep her from falling while she's asleep. A standard crib mattress is 51 5/8 by 27 1/4 inches with a thickness of 4 to 6 1/2 inches. Toddler beds can be inexpensive and made of plastic or more expensive and made of wood to resemble an adult bed.
Youth beds are bigger than toddler beds but smaller than twin beds. Youth beds measure 33 by 66 inches. Many parents don't buy these beds, because going from a toddler bed to a twin bed is much easier and less expensive.
Twin beds are 80 inches long and 39 1/4 inches wide. These beds do not generally have side rails, but they can be purchased separately and secured between the mattress and the box spring. If you have concerns about your child's readiness for a twin bed, consider placing the mattress or the mattress and the box spring directly on the floor until your child is used to the height of the new bed. Then, when the child gets older, put the mattress into a frame that will last him well into his teen years.
A few things to consider when you are making your decision are the size and age of the child, the size of the room and the needs of the household. If your child has already outgrown a crib, chances are she is too big for a toddler bed. There is no point in purchasing a new frame for a mattress that she's already too big for. If that is the case, check into a youth bed. If a youth bed seems too small or if you think your child will outgrow it too quickly, consider a twin bed with a plastic frame. These beds are often lower to the ground than typical twin beds but are large enough for an adult.