How to Measure a Kids Bike (Bicycle Sizing 101)

  • By: Kevinsmak
  • Date: January 12, 2023
  • Time to read: 11 min.
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To measure a kid’s bike, consider factors like:

  • The type of the bike
  • The age of the kid
  • Height of the child
  • The inseam
  • Their ability and maturity
  • The experience they have had with bike

The size of the bicycle’s tires is another factor to consider while selecting the best bike for you.

Choosing a bike that is suitable for your youngster might be challenging. It’s not always obvious where to begin when faced with the wide variety of sizes and brands on offer.

To help you pick the best bike for your youngster, we’ll go over some basic measurements below. We’ll discuss how to determine your child’s height, weight, and shoe size in order to get them fitted for the correct bike size.

What to Consider When Measuring a Kids Bike

With so many options, it’s not always easy to pick the right brand and size of kid’s bike.

Before we get into the specifics of sizing, let’s take a step back and look at some other things to keep in mind when purchasing a bike for a child:

The type of bike

The type of bike you intend to purchase will also affect what size bike is best for you. As opposed to a road bike, a mountain bike will require a different frame size.

Your child’s age

Age is an important factor to consider when purchasing a kid’s bicycle. This is because as children grow, they will need a bigger bike.

It’s important to choose a bike that your child will be able to grow into rather than one that they will quickly outgrow.

Your child’s height

Height is another important factor to consider when measuring a kids bike. You will want to ensure your child can comfortably reach the handlebars and pedals.

If they can’t, then the bike is too big.

Your child’s inseam

The inseam is the distance from the crotch to the ground of your child. You can use this measurement to establish the frame size of the bicycle.

You should check to see if your youngster can straddle the bike with their feet flat on the ground. The bike is too huge if they are unable to.

The child’s riding experience

A child’s level of riding expertise is another important factor to think about when purchasing a bike. It’s best to start them off with a smaller, less complicated bike.

You can upgrade to a more powerful bike as your child gains riding skills.

Kid’s maturity

Even if they are all the same age and height, children are not all the same. Some youngsters are more capable of handling a larger bike than others since they are more mature.

Whenever in doubt, it’s preferable to err on the side of caution and choose a smaller bike. Let’s talk about how to measure a child’s bike now that we are aware of the fundamental factors to think about.

How to Measure a Kids Bike

Here, we’ll go into more detail and examine how to gauge a child’s bike using the criteria we outlined above. In order for you to choose wisely when buying a bike for your child, we will provide you with as much information as we can. Here we go

How to gauge your child’s bicycle:

1. The Type of Bike

Many different types of kid-friendly bicycles exist, each one tailored to the needs of riders of a specific age bracket. Here are some representations:

Balance bikes (Age 2-4 years)

In essence, a balancing bike is a bicycle without pedals. If your child is just learning to ride a bike, this is the perfect model for them.

Their portability and modest weight make them simple to handle.

However, most balance bikes do not feature brakes. If you’re looking at purchasing a balancing bike for your kid, pick one with brakes so they can stop in an emergency.

Although brakes are always a good idea, they may not be necessary while the child is still small and you are around to keep an eye on them.

Small wheelers (Age 3-5 years)

A small wheeler is a bike with small wheels, usually 12-14 inches or smaller. This type of bike is great for kids who have outgrown their balance bike but aren’t ready for a bigger bike yet.

Small wheelers are lightweight and easy to control, which makes them perfect for kids who are still learning to ride.

They often come with a few features found on bigger bikes. They have pedals, coaster brakes, and sometimes even hand brakes. But since they have small wheels, they are not suitable for off-road riding.

Since they are transition bikes, you want to keep things as simple as possible. Avoid getting a bike with too many features that your child won’t be able to use yet.

Middle wheelers (Age 4-6 years)

These larger bikes are what we’ve been waiting for. Bicycles with middle-sized wheels measure between 16 and 20 inches.

When kids outgrow their balance bikes, they need to upgrade to something like this.

Lightweight and easy to operate, middle wheelers may travel quicker and over rougher terrain than small wheelers. The freewheel hubs and handbrakes on these bikes allow children to ride them without pedaling.

Middle-wheelers may have gears, but younger riders rarely require them. The purchase of a bike with gears, however, may be warranted if your child shows signs of becoming more daring.

In order to ensure your child’s safety, you should check their ability to ride a bike with a lot of speed before letting them loose.

Big wheelers (Age 5-9 years)

For convenience, I will refer to these as “giant wheelers” because I have seen some adults riding bicycles with such large wheels. Big wheelers, which have wheel sizes ranging from 20 to 24 inches, are essentially toy versions of full-size bicycles.

A bike like this could be ideal for your kid if he or she is taller than average or if they have a penchant for taking risks. They’re speedier and more capable than standard bikes on rough terrain.

They are about the same size as an adult bike, so when the time comes, they can make the smooth transition.

Big wheel bicycles typically include hand brakes and gears. Some of them even have suspension, which makes them perfect for rough terrain. Before letting your kid wild on a bike, be sure they know what they’re doing.


The prevalence of these bikes in the lives of today’s youth drove me to make a passing reference to them. BMX bikes are designed for racing and stunts. Thus, they normally have wheels between 20 and 24 inches in diameter.

These bikes may be the heaviest in the shop, but their durability more than makes up for their bulk. And a BMX bike is the greatest option if your kid is interested in racing or doing tricks.

Before buying a bike for your child, check to see if they are tall enough to reach the pedals. And if they want to do tricks, a bike with handbrakes is a good idea.

2. The Kid’s Age

In this article, we’ll examine the suggested wheel size and age range.

2-3 years

The appropriate wheel size here is 12 inches or 30cm. Since the kid is still young, you want to get a bike that is lightweight and easy to control.

A 12-inch bike is perfect for kids who are still on the balance bike.

3-4 years

Purchase a 14-inch bike that has several characteristics with larger bikes. Lightweight construction and coaster brakes are required.

Pedals are optional but could be included.

The time may come, as the child matures, to upgrade to a bike with hand brakes. Also, check to see whether the bike has a kickstand so your kid may leave it standing without worrying about it falling over.

4-5 years

A 16-inch or 41-cm bike is perfect for kids in this age group. The bike should be lightweight with coaster brakes and hand brakes.

Gears are not necessary but they may be included on some bikes.

You also want to make sure that the bike has a kickstand so that your child can park their bike without tipping it over. You can start introducing them to bikes with more features so they get used to them as they outgrow their smaller bike.

5-8 years

Get this kid a 20-inch or 51-cm bike. If they still like biking at this age, they should already be conversant with most features of a bike.

The bike, however, should still be lightweight especially if your kid is smaller in size. You don’t want them to be bogged down by a heavy bike.

The bike should come with almost all the features a bigger bike has. From handbrakes to gears and even a suspension system. However, if your kid isn’t into biking that much, then you can save some money by getting them a bike without all the bells and whistles.

8-11 years

A 24-inch or 61-cm bike is perfect for kids in this age group. This is the time when they are ready to transition into a bigger bike.

The bike should come with all the features of a bigger bike including handbrakes, gears, and even a suspension system.

This is also the age when you want to start looking at mountain bikes or BMX bikes if your child is into racing or tricks. Just make sure that the bike is lightweight and easy to control.

11+ years

Kids this age would do well on bikes with wheels larger than 24 inches (61 cm). It’s time for them to upgrade to a more capable bicycle.

3. The Kid’s Height

This is among the most important factors to consider when getting a bike for your kid. You don’t want them to be too cramped up or too stretched out on the bike.

Here is a general guide on how to choose the right sized bike based on your child’s height.

  • 36″-39″: 12-inch bike
  • 37″-44″: 14-inch bike
  • 41″-48″: 16-inch
  • 45″-54″: 20-inch
  • 49″-59″: 24-inch
  • 56″+: 26-inch

When sizing the bikes for their children, most parents opt to use the height. You could, however, be curious:

How can I measure my child’s height for a bike in the best way possible? As an example:

  • Have the kid stand straight against, say, a wall.
  • Use a tape measure to measure from the ground to the top of their head.
  • Record this measurement in both inches and centimeters.
  • You can use a meter rule if you don’t have a tape measure. Just make sure that you record and convert the measurement to inches, as most bike sizes are based on inches.
  • Use a bike size, most of which you can find online, to determine the appropriate bike size for your kid.
  • You can also use this guide to get an idea of what size bike your kid needs:

4. Your Child’s Inseam

The inseam is the distance from the crotch to the ground. To measure it, you will need a hardcover book and a tape measure. Here’s how to go about it:

  • With their shoes on, let your kid stand straight against a wall. Their feet should be slightly apart.
  • Place the book in between their legs at the crotch and have them hold it in place.
  • Use a tape measure to measure from the top of the book (the part that’s directly against their crotch) to the ground.
  • Record this measurement both in inches and centimeters. That’s the inseam.

Children’s inseams can now be measured. But how can you put that into practice to get them the right bike size? Let’s begin:

  • 14″-17″: 12-inch bike
  • 16″-20″: 14-inch bike
  • 18″-22″: 16-inch
  • 22″-25″: 20-inch
  • 24″-28″: 24-inch
  • 26″+: 26-inch bike

You should be careful not to pull the measuring tape too tightly when measuring the inseam. 

Additionally, be sure to gauge the inseam from their crotch rather than their waist.

A further consideration is the rapid growth of children. It is therefore recommended to choose the next size up even if you measure their inseam and they appear to fit nicely into a particular bike size.

They will have room to expand within the bike in this way.

5. The Kid’s Ability and Maturity

Kids develop differently and have diverse skills when it comes to playing with moving objects like motorcycles due to various biological factors. Therefore, even if your child is the same age and height as another child, it’s possible that they can’t ride bikes of the same size.

Simply put, some youngsters are more prepared than others to ride a larger bike. You should also take your child’s maturity and skill into account when selecting a bike size for them.

Go for it if they appear to be able to manage a larger bike.

However, if you believe they could benefit more from a smaller bike, choose that option instead. They shouldn’t ride the same size bike just because they are the same age or height as another child.

But how can you tell if your child is ready to ride a bigger bike? Here are a few advices:

  • They have lost interest in the bike they are currently riding and they seem to be ready for a change.
  • They have outgrown their current bike in terms of size and ability.
  • You can see them handle the current bike they are on better than you thought. For instance, if they are on a small wheeler that came with a brake, you may see them using the brakes well without any accidents. Or, they could start braking with their feet if the bike doesn’t have a handbrake.
  • You’ve seen them handle other moving objects well like scooters or skateboards. If they can control those, they can probably control a bike too.

In the end, only you know your kid best and whether they are ready for a bigger bike. Just use your best judgment, and don’t be afraid to go for the next size up if you think they are ready for it.

6. The Kid’s Experience

This is among the most obvious factors that will affect what size bike your kid needs. If they are new to biking, then they will obviously need a smaller and simpler bike to start off with.

As they gain more experience, they will be able to handle a bigger and more complex bike. So, if your kid is just starting out, don’t get them a big mountain bike thinking they will grow into it.

They won’t be able to ride it and they will probably get discouraged.

A good rule of thumb is to start them off with a bike that has 12-inch wheels. Once they have outgrown that, you can move up to a 14 or 16-inch bike.

However, other factors such as age and height still matter. You don’t want to buy an 11-year-old a bike that would best suit a 7-year-old even if they have ridden one before.

The best thing to do here is to look for an age-appropriate bike but with simpler features. Once they have gotten the hang of biking, you can then move them up to a bigger and better bike.

When in doubt, always go for the smaller size. It’s better for them to ride a small bike that they can handle than a big bike that they can’t. You can always buy them a bigger bike when they’re ready for it.


You’re well on your way to selecting the ideal bike for your child now that you know how to measure a kid’s bike.

You can pick the ideal bike for your child if you bear in mind all the variables covered in this article.

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