Car Seat Stage Calculator (Rear-Facing, Forward-Facing or Booster?)
Find which car seat stage fits your child — rear-facing, forward-facing with harness, booster seat or seat belt — from age, weight and height, following AAP and NHTSA guidance.
How it works
Under 1 year → rear-facing · Under 4 years and < 18 kg (40 lb) → rear-facing · Under 8 years and < 29 kg (65 lb) → forward-facing harness · Height < 145 cm (4 ft 9 in) → booster · otherwise adult belt, back seat until 13
The American Academy of Pediatrics (2018) advises keeping children rear-facing for as long as possible — until they reach the highest weight or height allowed by their convertible seat — then using a forward-facing seat with a five-point harness to its limit, then a belt-positioning booster until the adult belt fits, which usually happens at 145 cm (4 ft 9 in) and 8–12 years. NHTSA gives the same sequence by age. Seats differ, so the limits on your own seat’s label and your country’s law always take priority; the typical limits used here are a guide.
Worked example
A 3-year-old weighing 15 kg and 95 cm tall is under 4 years and under the typical 18 kg rear-facing limit, so the recommended stage is a Rear-facing car seat; the next step is a forward-facing seat with harness once the seat’s rear-facing limit is outgrown, and the child rides in the back seat until age 13.
Sources: American Academy of Pediatrics (HealthyChildren.org) — Car seats: information for families · NHTSA — Car seats and booster seats
Frequently asked questions
When can my child face forward in the car?
When they outgrow the rear-facing weight or height limit of their convertible car seat — for most children that is between 2 and 4 years. Rear-facing protects the head, neck and spine much better in a crash, so do not switch early.
When can a child stop using a booster seat?
When the adult belt fits properly, usually at 145 cm (4 ft 9 in) and 8–12 years: back against the seat, knees bending at the seat edge, lap belt low on the hips, shoulder belt across the chest and collarbone, and able to stay seated like that for the whole trip.
When can a child sit in the front seat?
The AAP and NHTSA recommend the back seat for all children under 13. Never put a rear-facing seat in front of an active airbag.
Are the rules different outside the US?
Yes. In Europe, i-Size (R129) seats require rear-facing until at least 15 months and boosters by height, and many Latin American countries set their own ages and weights. Always follow your local law and your seat’s manual.
Related calculators
This calculator gives general guidance for healthy children and is not medical advice. If you are worried about your child, or they seem unwell, contact your pediatrician, a nurse line or emergency services.