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Ultimate Guide To Kids Bike Sizes (And Bike Size Chart!)

Dec. 06, 2023
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The number one email question I get in my inbox: “What size bike does my kid need?”  Let’s be honest, it’s confusing!

For starters, kids bikes are sized differently than adult bikes (by wheel size rather than frame size).  Also, even when we’re talking about a bike with certain size wheels, the standover height and seatpost heights amongst manufacturers can vary drastically.

Finally, while a bike might be advertised for a 5-year-old, some 5 years olds are tiny while others are huge.  There’s no way those two kids will be best served by the same bike.

That said, you can figure out the right size bike without trial-and-error, or pulling your hair out.  We’ve helped hundreds of parents figure out which size kids bike to get.  Here are 3 tips to help you get the right size bike the first time.

1) Know What Wheel Size Your Child Needs

Kids bikes are “sized” by the diameter of their wheels.  The tiniest pedal bikes start with 12-inch wheels while bigger bikes go all the way up to 24-inch wheels.   When your kiddo is ready for 26-inch, they are generally ready for an adult size ride, although some bike manufacturers make smaller “youth” size 26″ bikes.

Balance bikes, on the other hand, start with wheels as small as 10″ although most balance bikes have 12″ or 14″ wheels.  

The best way to start narrowing down which size bike your child needs is to determine which size wheels they PROBABLY need.  I say probably because we’re basing it on an age range for kids of average height. 

If your child is tiny or super tall, they may need a smaller OR bigger bike than the general range we suggest here.  Don’t let that stress you out–this is just a starting point, so get a basic idea of what size wheels your kid PROBABLY needs.

Kids Bike Size Chart

Remember, this is just a starting point.  Use this chart to get a general idea of which size bike your child needs, but don’t skip the steps below!!!!

Wheel size Age Height Inseam 12” 2-3 2’10”-3’4” 14-17” 35-42 cm 14” 3-4 3’1”-3’7” 16-20” 40-50 cm 16” 4-5 3’7”-4’0” 18-22” 45-55 cm 18” 5-6 3’9”-4’3” 20-24” 50-60 cm 20” 5-8 4’0”-4’5” 22-25” 55-63 cm 24” 7-11 4’5”-4’9” 24-28” 60-72 cm

2) Measure Your Child’s Height and Inseam

The next thing to do is to measure your child.  Don’t skip this step or guess!

If you’re buying the bike as a gift, you should still be able to ask the child’s parents to measure them for you.  Lie and say you’re sewing clothes or something if it must be a secret!

Measure your child’s inseam AND their height.  You’ll want to take the measurements in inches (or convert to inches once you’re done). 

To measure your child’s inseam, have them stand against with their back against a wall, legs together, and place a book between their legs. Have them hold it as close to their crotch as possible. Then, using a pencil, mark where the top of the book hits the wall.

Make sure to write down those measurements and save them for our next step.

3) Look Up the Specs for the Bike (or Bikes) You are Interested In

Just because you think your child probably needs a 14″ bike doesn’t mean that ANY 14″ bike will fit them.  Different bikes have different stand-over heights and min/max seatpost heights.  It’s best to look for a bike that will provide the BEST FIT for your kiddo.

Not all bike manufacturers list the standover height for their bikes.  If they do, however, you should compare it to your child’s inseam.

The standover height is the height of the top tube of the bike frame where your child will be positioned when standing with one leg over each side of the bike.  This means that your child’s inseam needs to be AT LEAST as tall as the standover height.  Ideally, there will be a little more space than that for your child to maneuver the bike comfortably.

Your child needs to be able to comfortably stand over the top tube of the bike

The other stat that you should absolutely look up is the minimum seatpost height for any bike you are considering.  How the minimum seatpost height compares to your child’s inseam is dependent on whether you are buying a balance bike, first pedal bike, or a pedal bike for a confident pedaler.

For a balance bike, you want to make sure that the minimum seatpost height is no higher than your child’s inseam length.  This allows your child to put their feet flat on the ground, to learn to balance and to scoot.

So if the bike has a 12″ minimum seatpost height, then you need to make sure that your child has at least a 12″ inseam.  If not, look for a bike with a smaller minimum seatpost height.  

For a balance bike, you want your child to be able to place their feet flat on the ground while sitting on the seat.

If you are buying your child’s first pedal bike, then you want to make sure again that your child’s inseam is at as long as the minimum seatpost height or no more than 1″ apart.  This is because kids who haven’t learned to pedal yet, will want to be able to put their feet flat on the ground.  This gives them stability and the ability to “scoot” if they feel so inclined.

If your child already knows how to pedal (sans training wheels), then you can choose a bike with a minimum seatpost height that is 1-3″ higher than their inseam length.   This allows your child’s toes to touch the ground but not put their feet flat on the floor. 

This confident rider is at the small end of the size spectrum for this bike but is still able to comfortably reach the ground.

DO NOT buy a bike that has a minimum seatpost height any higher than 1-3″ longer than your child’s inseam.  They will not be able to touch the ground, will struggle to reach the pedals, and are probably going to struggle or get hurt. 

There are two ways to look up all information like minimum seatpost heights.  Your first option is to go directly to the manufacturer’s website.  Any decent brand is going to provide specs for their bikes.  If they don’t, don’t waste your time with their bikes.

Some manufacturers have even created special tools to help you pick the correct size bike for your child.  The Woom Bike Quiz or the Guardian Bikes RideSizer tool, for instance, helps you determine which size bike your kiddo needs online.  

The Woom size chart makes picking the correct size bike easy!

Your other option is to use one of our comparison charts.  For each child’s bike size, we’ve rounded up a list of some of the best kids bikes available and included a comparison chart with this info for you.  This is a quick and easy way to see which bikes will best fit your child.  

Balance Bike Guides & Comparison Charts:

Pedal Bike Guides & Comparison Charts:

What To Do When Your Child Is In Between Sizes

It’s pretty easy to choose a bike when your child fits nicely at the bottom end of the recommended height/inseam for a bike. It’s tougher when your kiddo is at the the upper end of the recommended height/inseam for a bike.

When this happens, we hear from lots of parents that they are worried that the bike won’t last very long, and that their child will outgrow it quickly. This is a valid concern, since neither bicycles nor money grow on trees.

If your child is pretty dang close to the next size bike, I generally tell parents to go ahead and size up. This is especially true if your child already knows how to pedal and is a confident rider.

You know your kiddo best. Are they athletic and capable of handling a bigger, heavier bike? Are they going to be confident standing on their tippy-toes or are they going to be scared?

If your child isn’t already a whiz on the bike, then consider staying on the smaller size bike, even if they will outgrow it soon. In this case, you might want to look for a used bike (or borrow a bike from a friend). You can buy an expensive bike several months down the line after they’ve had a bit of a growth spurt and are ready for the next size bike.

A Word On Kids BMX Bike Sizing

And now to throw a wrench into everything I’ve said above. If you’re buying a kids BMX bike, the above rules on bike size don’t apply.

There are two different types of kids BMX bikes: freestyle/street BMX bikes (that you would use at a skatepark for instance) and racing BMX bikes (which you would use on a race track). Both have different sizing.

For freestyle/street BMX bikes, you’ll generally want to choose a bike that has a wheel size one size smaller than you would for a traditional kids bike. In other words, if your child would ride a 16 inch bicycle, they’d want a 14 inch BMX bike.

Learn More:

For kids race BMX bikes, the wheel size is always 20 inches–even for really tiny riders. Only the frame size changes as your child grows.

There are five sizes of kids BMX racing bikes:

  • Micro Mini (under 5)
  • Mini (5-7)
  • Junior (7-9)
  • Expert (9-11)
  • Expert XL (10-13)

And here’s how they are sized by your child’s height:

SizeAgeHeightMicro Mini<53’6″-4’0″Mini5-74′-4’4″Junior7-94’3-4’7″Expert9-114’6″-5’5″Expert XL10-135’3-5’7″

Why Size Isn’t The Only Thing That Matters

Yes, size is the first thing to think about when picking out a kids bike but it certainly isn’t the only thing that you should be thinking about.  Once you know what size bike your child needs, you should begin thinking about things like weight (this one is a biggy), geometry, brakes, tires, whether or not to use training wheels, etc, etc, etc.

For more information on other things you should be considering, read our Guide To The Best Kids Bikes & How To Choose!

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    About Us

    The Rascals are a family of three. Kristen (mom), Blair (dad), and Parker (kiddo). We started Rascal Rides when Parker was born and we didn’t want to give up our passion for biking. As we learned, we shared. Over the years, we’ve tested hundreds of kids bikes, helmets, bike trailers, and more.

    Kristen is a USA Cycling certified coach and loves to share her passion for biking with other families. Blair is a bike geek, mechanic, and mountain bike junkie. Parker is our resident tester and inspiration.

    If you see us out on the trail, make sure to say hi!

    Children grow up fast, and finding a bike that fits them while offering a few years of service can be a difficult affair.

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    Whether you want to get them riding along with the family or commuting to school, making sure your little ones are comfortable on their bikes will help build their confidence faster.

    As with adult bikes, getting the correct size is vital for children’s enjoyment and for improving their confidence when they first start pedalling.

    The best children’s bikes will feature size-specific components such as child-size levers, cranks, saddles and handlebars to help your kids get the most out of their bikes.

    Most brands will recommend a height range for their bikes, while some suggest an age range, though this can be confusing because little riders grow at different rates.

    Wheel size remains an important indicator of children’s bike size, ultimately restricting the frame size.

    With all of this in mind, here’s everything you need to know about children’s bike sizes to make sure your kids feel safe and confident on their bikes.

    Kids’ bike size chart

    This table shows the various bike wheel sizes and the approximate ages they are suitable for, as well as the minimum height and inseam length for each wheel size.

    The important thing here is the size of the child, not the age.

    Measuring your child

    Getty Images

    The most important thing to consider when finding the right size bike for your child is not their age, but their size.

    Some brands will size bikes on overall height, though this doesn’t take proportions into account, so it’s important to also measure your child’s inside leg.

    This can be done by having your child stand against a wall with a book placed between their thighs. Once the height is market against the wall, measuring down to the floor with a tape measure will give you their inside leg measurement.

    The inside leg measurement will give you a good indication of standover height for younger riders, and where saddle height should be for older children looking for pedalling efficiency.

    Woom

    A smaller standover height will give your child more confidence when learning to ride because they will find it easier to put their feet down should they lose balance.

    While measuring your child will give you a good indication of what bike size you should buy, it is always best to sit your child on a bike before buying it to make sure they are comfortable and can reach the handlebars.

    What if my child is in between sizes?

    Getty Images

    It can be tempting to buy a bike that is slightly too big in the hope it will last longer before your child grows out of it, but this can compromise safety and stability.

    The more enjoyment they have when riding the bike, the more they’ll be interested in learning.

    Some brands have experimented with trade-up schemes, which enable you to return your bike and receive the next size up.

    Kids’ bike types and size guides

    Balance bike sizes

    Getty Images

    Balance bikes have become a very popular way of introducing young children to cycling, with the omission of pedals reducing the coordination needed to learn how to balance on two wheels.

    Similar to early Victorian bicycles, such as the dandy horse, balance bikes are propelled by kicking backwards and encourage the child to ride along at their own momentum.

    Most balance bikes will typically feature 12in wheels, making it easier for small legs to reach the floor, but make sure your child can support the bike and reach the brakes if they are fitted.

    If a child becomes confident on a balance bike, they can usually skip training wheels when progressing to a pedal bike because they will already understand how to balance it.

    First pedal bike sizes

    Immediate Media

    Whether they have mastered the balance bike or are using training wheels, making sure their first pedal bike fits will enable them to enjoy learning to ride a bike and the fun it brings.

    These bikes are usually designed for children who are 3 years old or above and typically feature 14in or 16in wheels, a low standover height and brakes – in line with the law for pedal bikes in the UK.

    As with balance bikes, it’s important your child’s feet can still touch the floor at this stage because sacrificing pedalling efficiency is well worth it for their security.

    First pedal bikes will usually be singlespeed, enabling young riders to focus on pedalling rather than changing gears, and can be heavy for their size.

    Kids’ hybrid bike sizes

    Islabikes

    Most children’s bikes will feature a hybrid design that enables young riders to explore trails while remaining efficient on the road.

    These multi-purpose bikes are designed for children aged six or older, with many featuring 20in, 24in or 26in wheels. They have low slung top tubes to allow for a lowered standover height.

    Kids’ hybrid bikes usually feature grip shifters that enable smaller hands with less dexterity to change gears easier.

    Kids’ road bike sizes

    Frog Bikes

    Kids’ road bikes usually feature cantilever brakes and large clearances to allow for knobbly tyres to be fitted for cyclocross.

    Road shifters can be hard to use with small hands, so make sure your child is confident with dropped handlebars.

    Kids’ road bikes are available in 24in, 26in and 650c wheel sizes, with the latter also being found on some women’s road bikes.

    If your child is confident on their road bike, then setting the saddle height as you would for an adult will enable them to be more efficient with their pedal stroke.

    Kids’ mountain bikes

    Specialized

    Kids’ mountain bikes come in all shapes and sizes, with the complexity of the bike differing between sizes.

    Some kids’ mountain bikes will feature suspension, though this can add weight to the bike, making it harder to pedal and manoeuvre.

    Instead of this, many brands offer wide tyres to soak up bumpy trails, while maintaining a light and playful bike.

    Kids’ mountain bikes are available in 20in, 24in, 26in and 27.in wheel sizes.

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    Hydraulic disc brakes can be set up with small reaches and provide the best braking for little hands.

    Ultimate Guide To Kids Bike Sizes (And Bike Size Chart!)

    Bike sizes for kids | How to find the right size bike for your ...

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