Child Car Seat Calculator: Which Car Seat for Your Child's Height and Weight
Free tool · Updated October 2, 2026 · By CouponTalk
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Quick answer
Choose a car seat by your child's height and weight, not only age. Babies travel rear-facing until at least 15 months, and longer is safer. Forward-facing harness seats suit about 76–105 cm and 9–18 kg. High-back boosters suit 100–150 cm and 15–36 kg. After about 150 cm, the car's own seat belt fits across the shoulder and hips.
How to use this calculator
- Measure your child's height standing against a wall, without shoes.
- Weigh your child, or use the latest weight from the doctor's visit.
- Check the label on the seat for its height and weight range before buying.
Car seat stages chart
| Seat type | Height (i-Size) | Weight (group) | Typical age |
|---|---|---|---|
| Infant carrier, rear-facing | 40–87 cm | Up to 13 kg (Group 0+) | Birth to 12–15 months |
| Convertible, rear-facing | 40–105 cm | Up to 18 kg | Birth to 4 years |
| Forward-facing harness | 76–105 cm | 9–18 kg (Group 1) | 15 months to 4 years |
| High-back booster | 100–150 cm | 15–36 kg (Group 2/3) | 4 to 12 years |
| Adult seat belt | Over 150 cm | Over 36 kg | 12 years + |
Always follow the height and weight limits on your car seat's label and the fitting steps in its manual.
Frequently asked questions
When can my baby face forward in the car?
Not before 15 months under i-Size rules. Experts recommend keeping children rear-facing as long as the seat allows, often up to about 4 years.
Should a child sit in the front seat?
No. Children are safest in the back seat, and a rear-facing seat must never go in front of an active airbag.
What is ISOFIX?
ISOFIX is a pair of metal anchor points between the seat cushions. Seats that click into them are easier to fit correctly than belt-fitted seats.
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