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Kids Bike Sizes Guide –A NEW Trick to Finding the BEST Fit

So your kid needs a new bike. But you’re wondering… what size bike does my child need?  Wheel size is the way that bike manufacturers classify their kids bike sizes, but it’s NOT the only factor! It’s not even the most important factor!

kids bike sizes image showing all sizes of kids bikes next to each other, starting at 12 and going to 24

Bikes with the same wheel size can vary drastically in overall size.  As a result, your child may fit on a 16-inch bike with one brand, but a 20-inch bike with another. There are even bike brands that offer small and large bikes within the same wheel size.

Kids Bike Sizes Chart

When selecting a kids bike, a child’s inseam and their height should both be taken into consideration in order to get the best fitting bike. Click on wheels size to see our top picks for each size bike.

Wheel SizeAgeInseamHeight
12″2 to 315″ – 18″36 – 39″
14″2 to 415″ – 20″37 – 44″
16″4 to 616″ – 22″41 – 48″
20″5 to 819″ – 25″45 – 54″
24″8 to 1123″ – 28″49″ – 59″
26″10 +25″ +56″ +

Visual learner? Here is a video walkthrough of our complete kids bike sizes guide. From measuring your child’s inseam to how to properly set the seat height on the bike, this 6-minute video will quickly answer all your questions.

Kids Bike Sizes: Four Steps to Finding the Right Size

Using your child’s inseam in relation to the bike’s seat height is the best and most accurate way to ensure a perfect bike fit.  The frame and the wheel size work together to determine the seat height of a bike. 

So by selecting a bike based on seat height, versus wheel or frame size, you can ensure a great bike fit for your child even if they’ve never had a chance to try out the bike before you buy it! This not only makes riding much easier, but all the experts agree a good bike fit is necessary for safety too!

young child standing next to her bike. Arrows indicating inseam measurement and bike seat height measurement to help find correct kid bike size

(1) Measure Your Child’s Inseam

While most bike manufacturers base their sizing on your child’s height, we always recommend using inseam instead. It’s much more accurate!

5 year old showing appropriate measurement for inseam, not height for choosing the right size bike for a kid
  • With shoes on, have your child stand against the wall, feet slightly apart
  • Place a hardbound book between their legs, spine towards the crotch
  • Raise the book until the spine of the book firmly hits their crotch
  • Level the book with the floor and measure from the ground up to the spine of the book – that’s the inseam!

(2) Narrow Down Wheel Size Based on Inseam

Using your child’s inseam, find the one or two wheel size categories they fall into. In general, as long as your child’s inseam is appropriate for the bike, it’s better to buy a larger wheel size. Larger wheels have more stability and allow more room for growth.

Kids Bike Sizes Chart showing sizing by wheel size, age, inseam, and height
Kids Bike Size Chart – Inseam Measurement is Key!

(3) Find the Perfect Seat Height (Using Child’s Inseam and Riding Ability)

Balance Bike

young child riding the a green bike sized perfect for her
young chil

While seated on the bike with their feet flat on the ground, a child’s knes should be slightly bent (in an athletic stance). The slight knee bend allow them to efficiently run on the bike.

SIZING TIP: The seat of a balance bike should be set 0.5 – 1.5” below the child’s inseam.

Bike with Training Wheels

Young child rider sitting on her bike with her feet touching the ground on her tip toes showing the perfect kids bike size for beginning riders

Kids should be able to touch the ground with their tip toes while sitting on the seat. For timid kids, touching with their feet flat is often preferred.

Kids usually stop the bike with the brakes, but they also need to able able to stop with their feet, especially while learning.

SIZING TIP: The seat of a bike with training wheels should be set 0 – 3” above the child’s inseam.

1st Pedal Bike (After a Balance Bike or Training Wheels)

Young child rider with feet flat on ground showing the perfect kids bike size for beginning riders

While learning to pedal a bike, a child’s entire foot should be able to touch the ground while seated on the bike. This allows them to easily stop and start the bike without falling off. Once they gain confidence, the seat can be raised for better leg extension and pedaling efficiency.

SIZING TIP: The seat of a child’s first pedal bike should be set at the same height as the child’s inseam.

2nd Pedal Bike (and Beyond!)

Young child sitting on her bike with her feet touching the ground on her tip toes showing the correct kid bike size for experienced riders

Kids should be able to touch the ground with only their tip toes. Setting the seat higher allows for proper leg extension for maximum pedaling efficiency.

SIZING TIP: The seat of a confident pedaler can be set 2 – 4” above their inseam.

(4) Buy for Current Fit and Growth

Your child’s bike should fit them now. If you buy a bike they’ll need to grow into, they’ll likely struggle to ride and have trouble building skills and confidence.

However, you do want to buy a bike that will last as long as possible. As a result, your child’s ideal seat height setting should be as close as possible to the bike’s minimum seat height.

So where do I find the best bikes and their seat heights?

Part of the reason that kids bike sizes are confusing is that there are no bike sizing “standards”. While the CPSC has rules regarding almost everything else about a bicycle, there are no rules about kids bikes sizes.

To make matters more confusing, most bike companies don’t publish the seat heights of their bikes! Not to worry, we’ve got you covered! We’ve measured the seat heights of over 50 different bikes for you!  

You can find seat heights on our comparison charts for each size bikes:

Other Kids Biking Resources

Guardian Bikes RideSizer: Enter in your child age and height and Guardian’s proprietary tool will tell you which size bike is best for them.

woom Bikes Size Finder: Take out all of the guess work of buying the right size woom bike with their bike finder tool.

For additional information on child bike sizes and what other features you should look for when shopping for a bike, check out our article Best Kids Bikes: The Authoritative Buying Guide.

For young kids that have never ridden a bike, a balance bike is likely a better option for them. Check out Why a Balance Bike Should be the First Bike for Your Toddler.

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