Kids Bike Sizes, by the Child
Children's bikes are sized by wheel diameter against the child's height — never by age. The chart above carries exactly the verified pairs, drawn plainly, and nothing else.
Height, not age
Age is a birthday; height is a measurement. Two children of the same age can stand a head apart, which is why the chart above does not mention age at all. Stand the child straight, measure, and read across — the wheel size does the rest of the talking.
The pairs, in words
At 85 centimetres of child, the chart says 12-inch wheels. By 95 centimetres it moves to 14-inch, and at 105 centimetres to 16-inch. A child of 115 centimetres pairs with 20-inch wheels, 125 centimetres with 24-inch, and at 135 centimetres the chart closes on 26-inch wheels — its last row. Those six pairs are the whole chart; it carries exactly what was verified and does not guess between the rows or beyond the ends.
Between wheel sizes
The temptation is always to buy the bigger bike for the growing into. Resist it. Between wheel sizes, the smaller bike the child can stand over safely wins — a bike the child controls today is worth more than one that fits some months from now. When the height sits near a boundary, stand the child over both if you can, and let standover settle it.
What this chart is
A starting size, read from height. It is not a fitting, and it does not know your child’s legs, confidence or hand span — the person in the shop holding the bike steady does. Take the wheel size in as a starting point, and let the child standing over the actual bike have the final word.