Car Seat & Bike Size Finder
Two of the questions every parent hits: which car seat now, and what size bike? Enter your child’s age and height for the right stage and wheel size, plus the safety milestone behind each.
Recommended fit
A belt-positioning booster raises the child so the seat belt crosses the shoulder and hips correctly — usually until about 145 cm tall.
A 16" wheel should fit. Set the saddle so the child can put the balls of both feet — or, when learning, both flat feet — on the ground, and always fit a helmet.
How the fit is decided
Height does most of the work for both answers. For the car seat, the tool combines age and height to point you to the right stage — rear-facing, forward-facing harness, booster, or seat belt alone — and once a child reaches roughly 145 cm the adult belt fits, so the booster comes out. For the bike, wheel size is matched to height so your child can reach the ground on the saddle.
These are starting points, not rules. The limits on your specific car seat and the sizing from your bike — plus a quick test ride — always take priority over any chart.
Frequently Asked Questions
When can my child move to the next car-seat stage?
The guiding principle is to keep them in each stage as long as they fit its height and weight limits — rear-facing as long as possible, then a forward-facing harness, then a booster, and finally the adult seat belt alone. Move up only when they've genuinely outgrown the current seat, not just because of a birthday.
When is a booster no longer needed?
When the adult seat belt fits properly on its own — usually around 145 cm (4 feet 9 inches) tall, which for most kids is somewhere between ages 8 and 12. The lap belt should sit low across the hips and the shoulder belt across the middle of the shoulder, not the neck. Kids under 13 are safest in the back seat.
How is bike wheel size decided?
Kids' bikes are sized by wheel diameter — 12, 14, 16, 20, 24, and 26 inches — and the best fit comes from your child's height, not just their age. When they sit on the saddle they should be able to touch the ground; a beginner wants flat feet down, a confident rider wants the balls of their feet.
Is this a substitute for the seat's own instructions?
No. This is general guidance to point you to the right stage and size. Always follow the height and weight limits printed on your specific car seat, the bike manufacturer's sizing, and your local laws, which vary by region.
General guidance only. Follow the height and weight limits on your car seat, the manufacturer’s bike sizing, and your local laws, which vary by region.