A safe crib mattress is firm, flat and a snug fit, with no more than two fingers of gap between the mattress and crib frame. Firmness is the priority for infant safety; soft surfaces raise suffocation risk. Look for CertiPUR-US foam and GREENGUARD Gold certification for low emissions.
For a baby, the crib mattress choice is about safety first and comfort second. The guidance below follows widely published infant-safety advice. Always follow your crib maker’s instructions and your pediatrician’s advice.
Firm and flat is the rule
Infant mattresses should be firm, not plush. A firm, flat surface supports safe sleep, while soft or contoured surfaces raise the risk of suffocation. Press the center and edges: a safe mattress springs back quickly and does not conform to the baby.
The fit test
The mattress must fit snugly. If you can fit more than two fingers between the mattress and the crib side, the mattress is too small. Gaps are a trapping hazard.
Materials and certifications
Look for CertiPUR-US foam, which limits harmful emissions, and GREENGUARD Gold, which tests for low chemical off-gassing, important in a small nursery. A waterproof, wipeable cover keeps the surface hygienic.
Dual-firmness and toddler use
Many crib mattresses are firmer on the infant side and slightly softer on the toddler side. Flip to the toddler side only when your child moves out of the infant stage, following the maker’s age guidance.
Browse all options in our crib and baby mattress reviews, and protect any mattress with the right cover from our protector guide.
This is general safety information, not medical advice. Follow your pediatrician and crib manufacturer guidance.
Frequently asked questions
How firm should a crib mattress be?
Very firm. Infant mattresses should be firm and flat to support safe sleep. The surface should spring back quickly and not conform to the baby’s body.
How do I know a crib mattress fits?
Do the two-finger test. If you can fit more than two fingers between the mattress and the crib side, the mattress is too small and creates a gap hazard.
What certifications matter for a crib mattress?
CertiPUR-US for foam emissions and GREENGUARD Gold for low chemical off-gassing are the most useful labels for a nursery.
