"The American Academy of Pediatrics recommends children remain in a rear-facing car safety seat as long as possible, until they reach the highest weight or height allowed by their seat."
For the typical “bucket” or “infant” car seat, the kind that is removed each time you get out of the car, that is typically around 22 pounds and 29 inches, although the limit varies from car seat to car seat, even when they are made by the same manufacturer.
The seat will have a sticker on its side that explicitly states the height and weight limits. For “convertible car seats,” the ones that can be used rear or forward facing, those limits are significantly higher and are also printed on the sides of the seat.
Reviewed by Dr. Sara Connolly, August 2019