A properly fitting bike allows a comfortable and safe sitting position for children as well as teenagers. The size of a child’s bike is usually based on the wheel diameter.
In adults, this is based on the frame size or seat tube length.
Proper bike fit allows the muscles can deliver optimal strength. This is less tiring and avoids overloading the knees.
How to size a kids/youth bike
Because children have less experience and balance, they are more susceptible to falls.
However, the habit of cycling is taught at a young age, and a seat tailored to a child’s height ensures optimum comfort and encourages them to ride on their bicycle.
All the while teaching them how to ride more intuitively. So how does one choose the right size of a child’s bicycle? Here is a table for a general rule.
|Age||Body Length||Bike Size|
|2-4 year||87-103 cm||12 inch|
|3-6 year||96-117 cm||14 inch|
|5-7 year||110-123 cm||16 inch|
|6-9 year||117-135 cm||18 inch|
|7-10 year||123-140 cm||20 inch|
|8-11 year||129-146 cm||22 inch|
|10-14 year||140-164 cm||24 inch|
|> 13 year||160-176 cm||26 inch|
Here is a graphic that describes the size of kids better. (I do not own the rights to this graphic, credit goes to http://www.wiggle.co.uk/)
Case 2: Size Based on Inseam and Height (More Advanced)
The size chart for children is based on age and height. Since not every child is equally tall at a certain age, it is better to choose the bike size based on body length.
A study  in which young children between 7 and 14 years show that choosing a bike just based on the bike size is not the proper way.
Along with the bike size, the most influential parameter for a sitting position is the inseam.
Kids Bike Size Chart
This is significantly different for children even of the same height. Based on the body size of 1,400 youth, one arrives at a conclusion summarized in the following table, which takes into account the growth:
|Body Length||Inseam||Bike Size|
|120-140 cm||< 52 cm||16 inch|
|52-74 cm||20 inch|
|> 74 cm||24 inch|
|141-160 cm||< 62 cm||20 inch|
|62-80 cm||24 inch|
|> 80 cm||26 inch|
|> 160 cm||< 74 cm||24 inch|
|>74 cm||26 inch|
The study was conducted with over 1400 young folks. 9 body measurements were taken, which in the end determined the size of the bike.
With these data, one could find out which size fits the children for anybody’s length. The only thing you need to adjust is the seat and handlebars.
A criterion of good seat height is the distance between the pedal and the saddle, corresponding to 88.3% percent of the inseam. Children between 120 cm and 140 cm tall fit so almost on a 20-inch bike.
For children between 140 cm and 160 cm, the average bike size is 24 inches. For teens bigger than 160 cm, the best fitting bike would be a bike with a wheel size of 26 inches.
Although most would prefer to go for the standard and easy to use first case, some like to go beyond paying close attention to detail and choosing the bike that would perfectly suit them.
This would require more hard work, but it would make your purchase all the more enjoyable in the end. You can always check out the comprehensive study referenced below for more information.
Kids Bike Sizes: How To Choose The Right Children’s Bicycle
 Laios L, Giannatsis I. 2010 Ergonomic evaluation and redesign of children bicycles based on anthropometric data. Appl Ergon 41: 428 – 435.
RoyalBaby Kids Bike Boys Girls Freestyle BMX Bicycle with Training Wheels Kickstand Gifts for Children Bikes 16 Inch Blue
15 used from $106.49
- 1. Easy to put together. 95% of the bike is assembled. Save your headache to install the front wheel and brake compared with 85% bikes. Assembly tools and an easy to follow instructions are included.
- 2. Safer riding! Safe grips and handbrake, Front caliper brake and rear coaster brake offer double safer, Wide 2.4” pneumatic tires add more stability, Sturdy steel frame,Crank, Non-slip resin pedal,Chainguard.
- 3. Easier to Ride! Your little ones will enjoy a smoother ride with Royalbaby sealed bearing since 2019, Royalbaby exclusive brake lever allows little riders brake efficiently.
- 4. Amazing design and color! Bright colors, stylish and charming. Bike bell and DIY decal add extra fun to the ride. Soft seat comes with a handle, which makes the bike easier to grab during teaching or loading.
- 5. More size options! 12,14,16,18,20 Inch available. Use our easy-to-follow size chart, you’ll find a perfect size for your little beloved. Note: Please take the kids height into consideration.
Schwinn Elm Girls Bike for Toddlers and Kids, 18-Inch Wheels, Pink
3 used from $104.39
- This Schwinn Elm girl's bike with 18-inch wheels is designed for children 3 - 7 years old or 42 - 52 inches tall. The Elm is perfect for riding to the park or riding on the sidewalk around the neighborhood
- With Schwinn's SmartStart Technology, this bike is designed just for kids: lighter frame, cranks and pedals are positioned forward, gearing designed for easier starting, narrower pedal positions, and smaller grips and seat
- Designed with younger riders in mind, this bike includes a rear coaster brake (reverse the pedals to stop) and a front caliper brake (hand-brake like adult bikes); easing the transition to a hand-brake-only bike when they’re ready
- The adjustable saddle, seat post, and slack seat-tube angle make for easy, tool-free adjustments to allow the Schwinn Elm girl's bike to grow with your child and prepare them for a full-sized bicycle
- Kid-Specific Q-Factor technology includes narrower pedal positions that match the width of a child's hips, allowing for easier peddling and handling
Schwinn Koen Boys Bike for Toddlers and Kids, 18-Inch Wheels, Blue
- This Schwinn Koen boy's bike with 18-inch wheels is designed for children 3 - 7 years old or 42 - 52 inches tall. The Koen is perfect for riding to the park or riding on the sidewalk around the neighborhood.
- With Schwinn's SmartStart Technology, this bike is designed just for kids: lighter frame, cranks and pedals are positioned forward, gearing designed for easier starting, narrower pedal positions, and smaller grips and seat.
- Designed with younger riders in mind, this bike includes a rear coaster brake (reverse the pedals to stop) and a front caliper brake (hand-brake like adult bikes); easing the transition to a hand-brake-only bike when they’re ready.
- The adjustable saddle, seat post, and slack seat-tube angle make for easy, tool-free adjustments to allow the Schwinn Koen boy's bike to grow with your child and prepare them for a full-sized bicycle.
- The Schwinn Koen boy's bike with 18-inch wheels comes ready to be assembled and includes the following: training wheels, saddle handle, kickstand, chainguard, and number plate.
JOYSTAR 12 Inch Kids Bike for 2 3 4 Years Old Girls, Kids Bicycle with Front Basket & Training Wheels for 2-4 Years Child, Pink
1 used from $85.18
- STURDY FRAME - Made of premium steel to survive the bumps of learning; Plus, the durable steel frame is backed by our limited lifetime warranty.
- COASTER BRAKE - This kids bike come with coaster brake, simply pushing the pedal backwards and stop the bike.
- SUITABLE FOR 2-4 YEARS GIRLS - 12" is for 2-4 years(33"-41") girls, comes with basket to transport their loved doll and training wheels for safe cycling.
- SHOCK PROOF SEAT - Shock-proof bike seat is bigger than normal seat, more comfortable for kids cycling.
- EASY TO ASSEMBLE - The kids bike is 85% assembled, come with basic assembly tools (PUMP NEEDED FOR THE TIRE).
Mongoose Switch BMX Bike for Kids, 18-Inch Wheels, Includes Removable Training Wheels
3 used from $96.56
- The Mongoose Switch Boy's Freestyle BMX Bike is great for first-time riders and comes with training wheels
- A low, stand-over steel frame allows for easy access and control for young children. A foot brake allows for confidence when stopping
- Styled like a pro rider's bike, this kid's bike features metal spoked wheels and black grips. An alloy four-bolt stem and four-piece handlebars adds strength for the ride
- The durable chain guard helps protect from scrapes and cuts, while the removable training wheels help first-time riders find their balance at their own pace
- This bike ships ready to be assembled and is ideal for riders between the ages of 5 and 7. Comes with Schwinn's limited lifetime warranty
Schwinn Toggle Quick Build Kids Bike, 16-Inch Wheels, Smart Start Steel Frame, Easy Tool-Free Assembly, Green
5 used from $125.87
- Schwinn Easy Assembly 16-Inch SmartStart steel bike frame is great for kids learning to ride. Fits ages 3 to 5, or 3’2” to 4’0”
- Lighter frame, narrower pedal positions, and smaller grips provide a more stable, confidence-building ride
- Simple single-speed drivetrain is easy to use. Intuitive rear coaster (pedal) brake delivers secure stops
- Kid-friendly saddle with handle for towing and storage. Adjustable seat post lets the bike grow with your child
- Quick Build tool-free assembly. Includes removable training wheels for learning riders