Car Seat Stages Explained: Infant, Convertible, Booster — and When to Switch
The AAP guidance in plain English, the limits of the eight seats we ranked, and the cheapest path through all the stages.
Stage 1: rear-facing (birth to 3–5 years)
The American Academy of Pediatrics says rear-facing until the seat's limit, not until a birthday. Infant seats (KeyFit 35, PIPA rx) go to 32–35 lb; convertibles here go to 40 lb (4Ever, Boulevard) or 50 lb (Extend2Fit, Foonf, Revolve360, Radian).
Stage 2: forward-facing with a harness (to 65 lb)
Every convertible and all-in-one here harnesses to 65 lb. Use the top tether every time.
Stage 3: booster (to 4 ft 9 in, usually 8–12 years)
All-in-ones (4Ever, Revolve360, Radian) include it; convertibles do not, so add a $30–$60 booster later.
The cheapest complete path
Chicco KeyFit 35 ($230) → Graco Extend2Fit ($200) → any high-back booster ($40): about $470 for two children's worth of use. Or one Graco 4Ever DLX ($350) from day one if you skip the carrier.
» See the full rankings: Best Car Seats of 2026, Best Convertible Car Seats, Best Car Seats for Extended Rear-Facing .