This depends on the carry position you choose. Most models come with suggested age windows for each position. Otherwise, there’s no limit except for maximum weight, which is again determined by the carrier’s features. As a rule, you’ll have to stop carrying your child as they reach 35+ pounds, which corresponds to 3-4 years of age. There are sturdier models like Baby Tula’s Free-to-Grow Carrier, however, which can hold up to 45 pounds.