How kids' bikes are sized
Children's bikes are sized by wheel diameter, not by frame size like adult bikes. The number you are looking for is the wheel size in inches, and it steps up as the child grows: 12, 14, 16, 20, 24 and 26 inch, after which a child moves onto a small adult bike. Getting the wheel size right matters more than the badge on the frame.
Kids' bike size chart by age
Use age as a starting point, then check the child can stand over the bike and reach the ground. As a rough UK guide:
- 12 inch wheels: around 2 to 3 years, roughly 85 to 100cm tall. Often a first pedal bike or a balance bike.
- 14 inch wheels: around 3 to 4 years, roughly 95 to 110cm.
- 16 inch wheels: around 4 to 6 years, roughly 105 to 120cm.
- 20 inch wheels: around 6 to 8 years, roughly 115 to 135cm.
- 24 inch wheels: around 8 to 11 years, roughly 135 to 145cm.
- 26 inch wheels or a small adult bike: from around 11 years and 145cm upwards.
Why inseam matters more than age
Children of the same age vary a lot in height, so a measurement beats a birthday every time. Measure your child's inside leg from the floor to the crotch with shoes on, and make sure they can stand over the top tube with both feet flat. On a first pedal bike they should be able to put both feet on the ground when seated. As confidence grows you can raise the saddle so only the toes touch, which is more efficient to pedal.
Cyclesite Tip. Do not buy a big bike for a child to grow into. A bike that is too large is harder to control and less safe, and it puts children off riding. Buy the right size now and size up when they outgrow it.
Buying kids' bikes used
Children outgrow a bike every couple of years, which makes buying new an expensive habit and buying used the sensible one. A used kids' bike in good order costs a fraction of new, holds its value well because the next size is always in demand, and can often be sold on again when outgrown. Check the brakes work within small hands' reach, the tyres and headset are sound, and nothing is bent.
Our used kids' bike guide covers the full checklist, and the bike size guide covers adult sizing for when they move up. When you are ready, browse used kids' bikes.
Common questions
What size bike does my child need?
Kids' bikes are sized by wheel diameter, not frame size. As a rough guide: 12 inch for ages 2 to 3, 14 inch for 3 to 4, 16 inch for 4 to 6, 20 inch for 6 to 8, 24 inch for 8 to 11, and 26 inch or a small adult bike from about 11. Measure your child's inside leg and check they can stand over the frame, as height matters more than age.
What age is a 20 inch bike for?
A 20 inch wheel bike suits most children from about 6 to 8 years, or roughly 115 to 135cm tall. Check standover clearance rather than going by age alone, because children of the same age vary a lot in height.
Should I buy a bigger bike for my child to grow into?
A little room to grow is fine, but a bike that is too big is harder and less safe to control. Aim for a bike they can sit on with both feet reaching the ground at first, then raise the saddle as they grow. Buying used makes sizing up every couple of years affordable.
Was this article helpful?
Related guides
Last updated · Editorial standards · Corrections