What Size Bike Should You Buy for Your Kid?

Bicycle fitter and Cycling Expert Mikael Hanson explains how bike sizing works for kids so that you can be sure you are getting the right size for your little one!

Two young girls riding bikes.

Photo by Amber Faust

As a bicycle fitter, it is a pretty straightforward process for me to determine the correct bike size for an adult. Starting with their height and factoring in their inseam, I can reliably arrive at the appropriate frame size. However, kids' bikes are sized differently and are sold based on wheel diameter/size (and not frame size). So, what is the right size bike for your child?

What Is the Proper Kids’ Bike Size?

A smiling child with a green bike.

Mikael's son gets a new bike! Photo by Mikael Hanson

Determining a child’s bike size is based on factors such as the child's age, inseam measurement, height, and level of ability. At the bottom, I have created a kids’ bike size chart to help you with your selection (and you will see that there are several different wheel sizes to consider).

1. Child’s Age

The first step is to use your child’s age to determine the starting point for their proper bike size (ie. wheel size - see the chart below). But this alone is not enough, as kids’ height can vary greatly for the same age.

2. Measure Height and Inseam

The next step is to use their height and inseam (the longest length of the inside of the leg) to further check if the indicated wheel size is correct. Both measurements should be taken while the child is barefoot. We want these measurements since a child’s height and inseam can vary greatly for kids of the same age, so these factors will further help determine if you are looking at the proper bike size.

An easy way to measure your child’s inseam: have your child stand barefoot with their back to a wall and feet a few inches apart.

  • Place a hardcover book between their legs with the spine facing upward.
  • Slowly lift the book as high as it will go.

Making sure the book is level to the ground, measure from the spine to the floor to arrive at the inseam measurement.

Diagram showing how to measure an inseam.

3. Check Stats on Bike

Next is to look at individual specs for the bikes you have in mind—as not all 14-inch bikes are the same. Additionally, manufacturers might have their own age and height recommendations for a particular bike.

The following figure shows the specifications for the Cannondale Kids 20-inch bike.

A chart showing the specs and measurements for the Cannondale Kids Trail 20 inch bike.

Specs for the Cannondale Kids Trail 20 inch bike

4. Stand-over Height

For a given bike, check the manufacturer’s stats (which can be found on their website). What you are looking for here is stand-over height, and compare that to your child’s inseam. This number needs to be less than their inseam measurement, thus leaving some space for the child to comfortably come down from the seat when stopping.

5. Minimum Seat Height

After looking at stand-over height, check the minimum seat height listed. For a child’s first bike, the minimum seatpost height should be within an inch of their inseam so that they can still touch the ground while sitting in the saddle. If your child already knows how to ride a bike, then the min seat post can be 1–3 inches higher than their inseam. For a balance bike, the seatpost height and child’s inseam should be approximately the same (but certainly not higher).

Kid’s Bike Size Chart

Chart showing how to size bikes for kids.

Proper Saddle Height

If your child is new to cycling, then they should be able to sit on the seat and have their feet flat on the ground (this allows them to stop by using either the bike’s brake or by placing their feet on the ground while maintaining balance). In this case, seat height and inseam are essentially the same. If your child is a more experienced rider, then they should be able to sit on the seat and have their tip toes touch the ground. In this case, the seat height is 2–3 inches more than their inseam measurement.

What if My Child Is Between Sizes?

This decision usually rests on how confident your child feels on a bike. If they are new to riding and need the comfort of being able to place their feet on the ground when in the saddle, then opting for the smaller size might give them more confidence (but could mean they grow out of the bike sooner). If your child is relatively confident on a bike, then select the next-larger size. If you are unsure on sizing, then please consult a salesperson at your local bike shop for assistance in choosing the correct size bike for your child.

If you are looking at new bikes, this is where a test ride from a reputable bike shop can be very helpful in the shopping process. They can help you choose between brands, wheel sizes, and proper seat height.

The Manhattan Fizz ZenCog Bike.

The Manhattan Fizz ZenCog Bike

Brake Type: Coaster vs. Handbrake?

A coaster brake (or foot brake) allows a child to stop by pedaling backward, which requires relatively little coordination to operate. If your child has strong coordination skills and is a more experienced rider who possesses the dexterity to operate a handbrake, then you should choose a handbrake over coaster brakes. A handbrake does not require a child to pedal backward to operate, so it is often the preferred brake for kids’ bikes.

Additional Accessories

Just like adults, kids will need a helmet and a bell or horn on their bike. Other accessories to consider to make riding for your child more enjoyable are a water bottle and cage, streamers for the handlebars, lights for the wheels or spoke covers, a light for the front of the bike if they plan to ride around dusk, front basket or handlebar bag, biking gloves, and sunglasses!

Connect With an Expert

If you do not have a local bike shop near you, you can always reach out to a Cycling Expert at Curated who will not only help walk you through these steps on determining your child’s proper bike size, but can also help you in the selection of the right bike and accessories. Cycling is a wonderful activity for the entire family to enjoy! My fondest memories as a child were those of my family doing group bike rides on some of the newly converted rail trails in southern Wisconsin—treat your kiddo to the same memories!

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Written By
After spending nearly 15 years working on Wall Street I was exhausted, bored and just a little a bit out of shape. With the blessing of my wife, I left the banking world in 2004 and started ENHANCE SPORTS - an endurance sports coaching and consulting company. A world champion, a few National champio...

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