What Is a Standard Crib Mattress Size?

Standard Size Crib Mattress

• Though some crib mattresses vary slightly in length and width, the majority of mattresses on the market are manufactured to a standard size that corresponds to standard-sized cribs. Standard measurements are 51 5/8 inches long and 27 1/4 inches wide. While mattress depth is less rigid, a mattress should never be greater than 6 inches thick. Foam mattresses may fall between 4 and 6 inches, while coil mattresses should be between 5 and 6 inches.

Measure

• Modern standard size mattresses do not often fit cribs built before 1974. To be 100 percent sure a mattress's listed measurements are correct, lay the mattress on a flat surface. Remove any bedding. With a tape measure, measure the mattresses width at the middle and from each edge.

The Finger Test

• To be sure the mattress is the right size for your crib, place the mattress inside the crib. Try inserting two fingers side-by-side between the crib rails and the mattress. If they fit, the mattress is too small. Room for one finger at most is acceptable. A mattress that does not fit all sides of a crib snugly may allow the baby to crawl underneath it.

The Crib Sheet

• Though mattress thickness is unimportant, the crib sheet should fit tightly over the mattress corners and remain there securely.

Toddler Beds

• Growing babies typically graduate from cribs to toddler beds. The good news for the family checkbook is that crib mattresses are the same size as toddler beds, so toddlers can continue to the same mattress once they graduate from the crib.