Kids bike sizes by height and age
Kids' bikes are sized by wheel size, and kids move through three or four sizes before they're teenagers. That's why there are so many good second-hand bikes about.
Rough guide by height
Height matters more than age. These ranges overlap, and every brand fits a little differently, so use them as a starting point.
| Wheel size | Rough age | Child's height |
|---|---|---|
| Balance bike or 12 inch | 2 to 4 | 86 to 102 cm |
| 14 or 16 inch | 3 to 6 | 99 to 117 cm |
| 20 inch | 5 to 8 | 114 to 132 cm |
| 24 inch | 7 to 10 | 127 to 150 cm |
| 26 or 27.5 inch | 9 and up | 146 cm and up |
Check the fit in person
Your child should be able to sit on the seat with the balls of both feet touching the ground, reach the bars without stretching, and pull the brakes with their fingers. If they're between sizes, a bike with room to raise the seat lasts longer.
What to check on a used bike
Squeeze both brakes and push the bike forward: it shouldn't roll. Spin the wheels to check they run straight. Look for cracks around the joints in the frame, and check the tyres for splits. Ask when it was last serviced. A bike shop tune-up is cheap compared with a new bike.
BMX and mountain bikes
BMX race bikes are sized by frame length (micro, mini, junior, expert and up) rather than just wheel size, so ask your BMX club. Mountain bikes add suspension and gears, so check that the shocks and gear changes work smoothly.