How Much Gap Around a Crib Mattress Is Safe?
No more than two adult fingers of gap between the mattress edge and the crib frame, on every side. If two fingers fit with room to spare, the mattress does not meet the safe fit standard and poses an entrapment risk.
The one thing to know: If you can fit more than two adult fingers between the mattress edge and the crib frame on any side, the mattress does not meet the safe fit standard; a 2022 CPSC rule also added a mandatory firmness test.
The firmness rule added in 2022
Beyond the fit test, CPSC approved a mandatory federal safety standard for crib mattresses in 2022 that added a firmness requirement: the mattress should not indent more than about 1/4 inch and should spring back quickly, because an overly soft surface increases suffocation risk for an infant face-down.
How to check your crib and mattress together
Always use the mattress sized specifically for your crib model -- mismatched mattress and crib sizing is the most common way the two-finger gap rule gets violated. Test the fit on all four sides, not just one, and recheck after any time the mattress is removed and replaced.
Always follow your product's manual and current CPSC/NHTSA guidance; this page summarizes published standards and is not a substitute for them.
Frequently Asked Questions
No more than two adult fingers of gap between the mattress edge and the crib frame, on every side. If you can fit more than that, the mattress does not meet the safe-fit standard.
A 2022 CPSC federal safety standard for crib mattresses added a mandatory firmness test, requiring the mattress to not indent more than about 1/4 inch and to spring back quickly, because an overly soft mattress poses a suffocation risk.
No -- always use the mattress sized for that specific crib model. A too-small mattress in a larger crib frame is one of the most common ways the two-finger gap rule gets violated.
The general safe-fit principle (no dangerous gap around the mattress or pad) applies across infant sleep products, though the specific federal standard cited here (the 2022 rule) is for crib mattresses.