What Are the Different Kids' Bike Sizes?

Dan Cavallari

Unlike adult bikes, which are measured by the wheel size and the frame size, kids' bike sizes are usually determined only by the wheel size. The wheel sizes are usually measured in inches, and the most common kids' bike sizes are 12 inch (30.5 centimeters), 16 inch (40.6 centimeters), 20 inch (50.8 centimeters), and 24 inch (61 centimeters). Some larger children may even fit a 26 inch (66 centimeter) bike, which is considered an adult-sized bike; at that level, the size of the bike will also be measured according to the frame size. The smallest children will ride 12 inch bikes, which usually feature training wheels and may or may not feature pedals.

Small children's bikes are typically as small as 12-inches in diameter.
Small children's bikes are typically as small as 12-inches in diameter.

12 inch (30.5 centimeter) bikes are meant for children who have not yet learned to ride bikes on their own. They are low to the ground to accommodate the small stature of young children, and even though the kids will not be able to reach high or even moderate speeds, helmets should always be worn while riding. The next step up in kids' bike sizes is the 16 inch (40.6 centimeter) bike; 14 inch (35.6 centimeter) bikes do exist, but they are not nearly as common as other sizes. The larger wheel size will also translate into a slightly larger frame, and these bikes are also likely to feature training wheels to help kids learn to ride properly.

Choosing the correct size bike for a child's age may reduce the chances of injury.
Choosing the correct size bike for a child's age may reduce the chances of injury.

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The next step up in kids' bike sizes is the 20 inch (50.8 centimeter) bike. This bike will feature larger wheels that are the same size as BMX wheels. The frame of such a bike is likely to be far smaller than a BMX frame but larger than a 16 inch (40.6 centimeter) kids' bike. By this time, kids can usually ride on two wheels, though it is still possible to put training wheels on this size of bicycle. Training wheels can also be installed on 24 inch (61 centimeter) bicycles, though again, they are not usually needed.

24 inch (61 centimeter) and 26 inch (66 centimeter) kids' bike sizes may or may not be considered exclusively kids' sizes at all. Many adults ride 24 inch (61 centimeter) bikes, and the vast majority of adult riders will fit a 26 inch (66 centimeter) bike. The frame sizes of these two types of bikes are also likely to change, allowing for a more accurate fit for larger children or adults.

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Discussion Comments


@clintflint - It's not that hard to find a kid's bike size calculator online, so no one really has an excuse for getting a bike the wrong size.

I think the only reason it happens is because someone will see a secondhand bike for sale or maybe a good deal in a store and will just guess at the size they need.


@indigomoth - Even if your kids are very confident on a bike you still have to make sure they have the right size. If you aren't sure about it, ask someone at the store about their bike sizes for children or do some research on it.

Confident kids are more likely to experiment and can just as easily end up crashing or needing to stop suddenly, so don't think you can give an advanced person a bike that is too big or too small and they will just make it work.


I think the best thing to do is to get your kids to stand over the bike in the store. You want to get something that is right on the cusp of their size, so that you won't have to get another one for a few years.

But make sure they can sit on the seat and still put their feet on the ground without falling over. This is pretty important, especially if your kids are not good at cycling, because it helps them with confidence. A kid's bike size chart can help, but I don't think there is any substitute for taking them into the store and getting to see how comfortable they are on different sizes.

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