Most kids try a two-wheeler with training wheels around age 3 years. Between ages 4 and 8 years most kids develop sufficient skill to ride without training wheels, and sufficient hand strength to safely use hand brakes instead of a coaster brake.
Adult bikes are sized by the frame (measured from the center of the bottom bracket to the top of the seat tube). Bikes for children are sized by their wheels: 12”, 16”, 20” and 24”.
|Child’s Inseam||Approx. Age||Wheel Diameter||
|14-17 inches||2-4 years||12 inches||Most come with training wheels, some are direct drive.|
|18-22 inches||5-8 years||16 inches||Rear coaster brake and pneumatic tires, some have front hand brake.|
|22-25 inches||7-10 years||20 inches||Multi-speed with hand brakes.
|24-28 inches||9+ years||24 inches||Most features match those of an adult bicycle.|
The rider should be able to dismount and comfortably straddle the bike flat-footed. And then with a slight lean of the bike, slide onto the seat, put their foot on a pedal and, when the skill is there, ride away.