Kids' bike sizes are best determined by wheel size. This directly correlates to the frame size: as the diameter of the wheel increases, so does the frame size of the children's bicycle. You can often estimate what size bike your child will need based on their age, but the best way is go by their height.  Kids’ heights can vary quite a bit, what with the growth spurts and all, so using their height instead of age will provide a much more accurate way to determine the appropriate bike size.  And of course, you should have your child test ride the bike before purchase when possible.

Check out our handy size chart to determine the right size for your child.