Convertible Car Seats

Convertibles use a built-in harness; boosters use your seat belt. Convertibles work from birth through about 65 pounds, starting rear-facing and switching forward-facing with a 5-point harness. Boosters take over after that, raising your child so the vehicle's lap and shoulder belt fits correctly. High-back boosters add head and neck support; backless boosters come later for taller kids.

A booster seat is next. Once your child outgrows the convertible car seat's forward-facing harness limits, usually around 65 pounds, they move into a booster that uses the vehicle's seat belt instead of a 5-point harness. High-back boosters come first and provide head and neck support, then backless boosters once your child is taller and the vehicle's seat belt fits correctly across the shoulder and lap. Some all-in-one car seats skip the separate purchase by converting straight into a high-back booster.

Switch when your baby outgrows the infant car seat's height or weight limit, whichever comes first. Most infant seats top out around 30 to 35 pounds and 30 to 32 inches tall, which many babies reach between 9 and 18 months. Signs it's time: the top of your baby's head is within an inch of the seat shell, their shoulders sit above the top harness slot, or they exceed the listed weight. The convertible seat should still be installed rear-facing until at least age 2.

Yes, when the seat is rated for newborns and a proper infant insert is in place. Most convertible car seats fit babies starting at 4 or 5 pounds rear-facing, with a removable infant insert that positions a newborn correctly. The trade-off is that convertible seats stay in the car and don't click into a stroller, so many parents still start with an infant car seat for the carrier convenience and switch to a convertible later. Either path is safe as long as the seat fits your newborn's weight and height range.