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Kids’ bike size chart: what size bike does my child need?

Start with height and inseam, use age only as a rough check, and never buy a bike a child has to grow into.

By Dennis, from Atlanta · 4 min read

Two kids ride bikes of different sizes at a bike rodeo: a 20-inch and a small bike with training wheels — Photo: Fort Drum MWR · Public domain

Buying a bike for a kid is one of those things that looks simple until you actually do it.

A 20-inch bike sounds like it should fit a 20-inch-sized kid. It does not. Age charts help, but two seven-year-olds can be completely different sizes. And the old advice to buy a bike a child can grow into is especially unhelpful when the goal is for that child to actually enjoy riding it.

The better way to size a kids’ bike is to start with height and inseam, then use age only as a rough check.

A simple kids’ bike size chart

Wheel size	Typical height	Typical age	Good for
12-inch	34–40 in.	2–4	Balance-bike stage
14-inch	37–43 in.	3–5	First pedal bike
16-inch	40–46 in.	4–6	New independent riders
20-inch	45–52 in.	6–8	Longer rides, gears, school routes
24-inch	49–57 in.	8–11	Stronger riders, longer distances
26-inch / small adult	55 in. +	10+	Older children and teens

Every range in that table is an approximation. Treat it as a starting point, not a substitute for trying the bike.

The American Academy of Pediatrics recommends buying a bike that fits now, rather than one a child has to grow into. An oversized bike is harder to control, especially for a newer rider. The AAP also recommends bringing the child along when shopping so they can actually try the bike.

Measure inseam, not just height

If you only measure one thing, measure the inseam.

Have your child stand in socks with their back against a wall and feet a few inches apart. Place a hardcover book between their legs, gently raise it to mimic a saddle, and measure from the floor to the top of the book. Then compare that number with the manufacturer’s minimum saddle height.

For a newer rider, I err on the side of a little more foot contact with the ground. Confidence matters. A child who feels trapped on top of a bike that is too tall may technically fit according to a chart and still hate riding it.

Don’t assume bigger wheels are better

Parents understandably want a bike to last. Kids grow quickly, and good bikes are expensive.

But a bike is not a winter coat.

If your child cannot comfortably start, stop, turn and put a foot down, saving a few months of growth is not worth it. This matters even more if the bike will be used around traffic, on a school route, or in a group. The AAP is blunt about oversized bikes: a child without the skills and coordination for a bigger bike may lose control of it.

What size bike is best for a bike bus?

There is no special bike-bus size. The right bike is the one your child can control well for the full route.

Before joining a bike bus, a child should be comfortable starting without help, braking smoothly, holding a predictable line, turning while staying in control, looking ahead instead of down at the front wheel, and riding the expected distance. For many elementary-school children that ends up being a 16-, 20- or 24-inch bike, depending on their size.

Weight makes a noticeable difference too. If a child weighs 45 pounds, the difference between a 17-pound bike and a 30-pound bike is meaningful: starts, hills, handling, and how tiring the ride feels.

Check the fit again after a growth spurt

Kids don’t grow in a smooth line. They show up at breakfast one morning and none of their pants fit. Bike fit changes the same way. Every few months, check:

Saddle height: can they start and stop confidently?
Reach: are they stretched forward to get to the bars?
Brakes: can they comfortably reach and operate the levers?
Knees: coming absurdly high at the top of the pedal stroke?
Control: do they look relaxed, or are they fighting the bike?

Sometimes a small saddle adjustment is all it takes. Other times it really is the next wheel size.

Fit matters more when the ride has a destination

A five-minute loop around a cul-de-sac is forgiving. Riding to school is different: backpacks, hills, intersections, other riders and a clock. NHTSA’s first piece of bicycle-safety advice is refreshingly simple: ride a bike that works, and one that fits.

If you are getting a child ready for a bike bus, do a practice ride before the first school morning; it answers more than any chart can. Then see whether a bike bus already rides to your school. If there isn’t one yet, here is how to start one. Still working on the riding itself? Start with teaching a kid to ride without turning it into a battle.