Kids Bike Sizes: 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!

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.

The age of a child is also typically not a good indicator of size. One 5-year-old may fit on a 16-inch bike while a 4-year-old may fit on a 20-inch bike! So what’s the best way to determine a kids bike size? With our simple tricks, finding the perfect size bike for your child is quick and easy.

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

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 – 3 years15″ – 18″36 – 39″
14″2 – 4 years15″ – 20″37 – 44″
16″4 – 6 years16″ – 22″41 – 48″
20″5 – 8 years19″ – 25″45 – 54″
24″8 – 11 years23″ – 28″49″ – 59″
26″10 + years25″ +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 age, 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!

5 year old 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 age or 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 bike 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.

For example, our 5-year-old shown above has an inseam 19.5″ inches. Based on the bike size chart below, she could on THREE different size bikes! The larger wheels of the 16″ and 20″ however, will be much better for her as she grows. The next step will help determine which of these two sizes is best.

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)

Now that you know what size(s) bike is likely best for your child, it’s time to take your child’s riding ability into consideration. Why? The proper fit of a bike is based on the seat height of the bike as compared to the child’s inseam. The seat height of a bike, however, should be set differently based on if your child is a beginner, is experienced, or is using training wheels.

The seat height is the distance from the ground to the top of the seat and will help you narrow down your options even further and guarantee a great fit from day one!

Beginning Riders (1st Bike After a Balance Bike or Training Wheels)

5 year old rider with feet flat on ground showing the perfect kids bike size for beginning riders

A beginning rider (including balance bike graduates) should be able to sit on the bike’s seat and have their feet flat on the ground. At this stage, it’s essential for a child to be able to easily stop their bike using their feet. As a result, their bike’s seat height should be set equal to their child’s inseam.

In the image above, our 5-year-old tester is on a 16 inch bike with the seat height set to 19.5″ to match her inseam. If she were a beginning rider, this bike would be a perfect size bike for her.

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

Experienced Riders – 2nd Pedal Bike (and Beyond!)

5 year old sitting on her bike with her feet touching the ground on her tip toes showing the correct kid bike size for experienced riders

An experienced rider, who knows how to comfortably start and stop a bike as well as use either a hand brake or a foot brake, should be able to sit on the bike’s saddle and have their tip toes touch the ground. This means that the seat should be set 2 to 4 inches ABOVE the child’s inseam.   Raising the seat allows for proper leg extension while pedaling, which maximizes the efficiency of each pedal stroke.

If our 5-year-old tester was an experienced rider, this 20 inch bike with the seat height set to 22.5″ (3 inches above her inseam) would be a perfect fit.

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

Beginner Bike with Training Wheels

5 year old rider sitting on her bike with her feet touching the ground on her tip toes showing the perfect kids bike size for beginning riders

For those who plan on using training wheels, feet flat or tiptoes both work, depending on the confidence of your child. Because the child doesn’t have to balance the bike or worry about falling over as much, just set the seat according to what is most comfortable for them.

This typically means that the seat should be set 0 to 3 inches above the child’s inseam.  For timid kids, setting the seat lower so they touching with their feet flat is often preferred.

With more aggressive riders, setting the seat higher allows for greater pedal efficiency so they can rider faster, but he cautious not to set the seat too high, as many kids on training wheels still instinctively stop the bike with their feet.

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

Balance Bike

If you happen to be looking for a balance bike, be sure to check out our balance bike sizing guide. For a quick reference though, the seat of a balance bike should be set 0.5″ to 1.5″ below a child’s inseam.

young girl riding the Subrosa altus balance bike

While seated on a balance bike with their feet flat on the ground, a child’s knees should be slightly bent (in an athletic stance). The slight knee bend allows 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.

(4) Buy for Current Fit and Growth

Now that you know the desired seat height for your child’s bike, you can begin shopping for your bike! Ideally, you’ll find a bike that has a minimum seat height that’s as close to (but without going over) the seat height you determined in step 3.

This allows the bike to fit perfectly now, but also offers the most room for growth so you don’t have to buy another bike too soon!

Here’s an example using the bikes we just saw and our 5-year-old tester. Each of the following bikes are a great fit for a child her size, but which one is best depends on the child’s experience and riding ability.

  • Pello Revo 16″ (bike shown in the Beginning Riders section) has a minimum seat height of 19.5”
  • woom 4 20″ (bike shown in the Experienced Riders section) has a minimum seat height of 22”.
  • Schwinn 16” (bike shown in the training wheels section) with a minimum seat height of 21”.

If our 5-year-old tester is a beginning rider, the Pello Revo is a perfect fit because its minimum seat height matches her inseam and allows her to sit with her feet flat on the ground.

If she is experienced, the woom 4 is a much better option. With its minimum seat height set 2.5” inches above her inseam, she can sit on the saddle and reach the ground with her tip toes. And it offers plenty of room for her to grow!

Lastly, if she is using training wheels, the Schwinn 16 is a great option for her if she is an average or confident rider. With a minimum seat height set 1.5″ above her inseam, she can comfortably reach the ground with low tip toes.

When selecting your child’s bike be sure to narrow down several options so that other factors such as price, weight, brake type and even color preference can also be taken into consideration.

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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