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What is the standard Baby Crib Mattress Size?

In 2008, the United States Consumer Product Safety Commission passed the Consumer Product Safety Improvement Act (CPSIA).

Crib mattresses are now federally regulated and, as with cribs, must pass rigorous standards to ensure safety. The heavily regulated baby crib mattress size “prevents head entrapment and suffocation between the mattress and crib sides” (

The minimum size for a crib mattress is 27 1/4” x 51 5/8” and should not exceed 6″ thickness. 

The parent rule of thumb to ensure your crib mattress is the proper fit is the two-finger test. You should not be able to place two fingers between the crib slats and your baby’s mattress. The snugger the mattress, the safer the sleeping area is for baby, and greater peace of mind for you!

Looking for a crib mattress for your nursery? Learn more about choosing the right mattress on our Best Baby Mattress recommendation page.