All little riders grow at different rates. So the best way of finding the right size bike for them is to look at models in their age range and then match their height to the right bike. Kidâs bikes are basically scaled down versions of adult bikes and are typically measured through wheel sizes. As a rule, itâs best to get your child to sit on a potential new bike and to check that they can touch the ground with both feet. For more information about choosing kid's bikes visit our buying guide.