If you were asking about the ages of children, Geiger, a certified child-safety seat installation technician, says the laws are different in each state, but as a general rule it isn't safe for a child to be secured only with a seat belt until they are at least 8 years old or 4 feet 9 inches tall.
The Insurance Institute for Highway Safety maintains a list of child-restraint laws by state that should explain the requirements where you live.
As kids grow, parents have to decide when it's time to transition from an infant seat to a convertible seat, then to a booster and — finally — when they can be secured with just a seat belt. Here are helpful tips on making that first step out of an infant seat and then taking the final big step out of a booster.Related
Car Seat Basics Part Two: From Infant to Convertible Seat
Car Seat Basics Part Three: Beyond the Booster
More on Child Safety from IIHS