Bike Size Guide For Kids: How to Find a Kid’s Bike that Fits

Buying a bike for your child is significantly different from buying adult bikes. Unlike a mountain bike that comes in standard sizes for enthusiasts, buying a bike for your child involves a lot more variables.

Selecting the right bike for your child turns out to be a lot like shopping for their clothes and shoes. Similar to these commodities, kids’ bike sizes vary depending on the child´s height and age.

This is where things get a little complicated. Contrary to popular belief, standardized bike sizes for children don’t exist. Different bike manufacturers make differently sized bikes for kids of the same age.

Hence, if an adult is unable to select a new bike based on the age of their kid, what else should he look for in order to get a kids bike of the correct size?

Thankfully, choosing the right size of a bike is actually a lot easier than it is made out to be. Owing to the methods highlighted in the guide below, every adult can now select their child´s first bike accurately and with peace of mind.

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How to Choose a Kid’s Bike that Fits

Wheel Sizes

As a starting point, a popular metric of determining the right-size bike for kids has always been the wheel. The wheel size is basically the diameter of both the wheels of the kids’ bike.

Kids’ bikes come in a variety of wheel sizes: 12-inch wheels, 14-inch wheels, 16-inch wheels, 20-inch wheels, and 24 inches. As the wheel gets bigger, so does the bike frame accommodating it.

The wheel size has been a widely used metric for quite some time now and is used with two other factors, age and height, to correctly determine the optimum bike size for kids of all ages.

Age and Height

Every popular kids’ bike size chart correlates height range and age range to wheel size. As a child´s height increases with age, so does the bike to cater to his or her large frame.

Such charts are widely displayed in every bike store and are designed to help parents determine the best training wheels for their children. These charts typically provide wheel sizes for children who are between 1 year old and 14 years old.

However, seldom do they work as they are supposed to. A child may be part of a particular height range and also be of the same age as in the chart but still may find it difficult to ride a bike recommended by the data chart.

Why is this so? Why isn’t the data chart accurate?

The kids’ bike size chart doesn’t seem to work because it draws its conclusions from the wrong set of data. Kids grow at different rates and their heights and age sometimes don’t correlate due to this variable rate of growth.

As a result, a 20-inch size bike could be ideal for kids of two different heights. This difference arises because such charts don’t account for the seat height and wheelbase.

Two bikes of the same wheel diameter (say 20-inch size) can have totally different seat heights. This means kids of two particular heights and ages will fit on a bike of the same frame size.

Since there’s only limited adjustment available on a seat post, this means that the bike size chart doesn’t work.


If wheel size and child height cannot be an accurate barometer of finding the right-sized bike, what is a great alternative then?

The solution lies in what’s called the inseam. If you want the find a bike that fits, you need to measure your child´s inseam.

To measure your child´s inseam the best way, he or she needs to stand upright with his or her back to a wall. The feet should be at a distance of at least 6 inches from each other, and the child should be wearing the same shoes or joggers that they would normally wear on a bike.

Take a measuring tape and measure the inwards length of the child’s pants from their crotch right down to their feet. This is the inseam.

Measuring your child may seem somewhat technical for a sport but it’s one of the most accurate ways to ensure perfect bike sizing.

A further level of accuracy in inseam measurement can be achieved by using any book of at least one-inch thickness.

Place the book between the legs with the spine of the book towards the crotch. Make sure to push the book upwards till the spine of the book meets the crotch.

Now, place the tape at the spine of the book and measure the distance to the ground below. The measuring tape should be perpendicular to the ground to ensure accurate sizing. 

Now that the child´s inseam has been found, it’s time to refer to the kids’ bike size chart again.

Determine the wheel size that falls best within the inseam range. If the child´s inseam falls at the end of the range, select the next biggest wheel size.

This is to allow for the child’s growth. Children grow bigger with time and thus, a bike should accommodate for this increase as much as it can.

Also, a larger bike has larger tires that are more stable. This may help prevent accidents as well by allowing the child to have greater control of the vehicle he or she is driving.

Types of Kids’ Bikes

Now that you’ve found the inseam, it’s now time to find the perfect type of bike for your kid.

It’s important to introduce children to bikes in a way that feels natural, and you can do that by choosing bikes that are easier to ride. This riding difficulty should then progressively increase as the child gets older.

Children who are just starting are usually encouraged to begin with balance bikes or training wheels with a moderate standover height before transitioning to pedal bikes.

Balance Bikes

A balance bike is generally a bike without training wheels to enable children to develop confidence in pedaling. Without the safety of training wheels to fall back on, balance bikes ensure that children can use their feet to run the bike or as brakes.

When a child is seated on a balance bike, he or she should have their feet flat on the ground with moderately bent knees for good feet movement.

Ensuring that a kid can touch the ground firmly while on the seat post provides the child with confidence that they would be able to use their foot if they feel that control of the bike is slipping away from them.

On balance bikes, the difference between inseam height and seat height should be around 1.5 inches.

Training Wheel Bikes

An alternative to balance bikes are bikes with training wheels. These bikes are a little higher as the seat post is longer than the inseam by about 3 inches.

With wheelies for added safety, the saddle height should be such that children are able to touch the ground with only their toes.

Training discs are there to provide ease and comfort to a child who is just starting out. Knowing that such discs would prevent the bike from tipping if he or she lost pedal power, the child gradually finds the confidence to leave these training discs with time.

Training discs remove the greatest fear among children when riding; that they would hurt themselves if they aren’t able to balance the bike properly.

The presence of training discs coupled with the increased height enables children to gradually let go of this fear of a potential accident if they let their toe off the ground.

Pedal Bikes

Once a child has had sufficient experience over either of the two types of bikes above, they should transition to pedal bikes. For their first pedal bike, the leg length is the same as saddle height.

This means that the child’s foot should be on the ground when the leg is straight. This is to enable children to gain confidence while riding without training wheels.

Children can easily use their legs to stop this first pedal bike which will give them peace of mind.

The seat height could be gradually increased on the pedal bike as the child becomes more confident and grows with time. Eventually, this leads to the second pedal bike where the seat height is up to 4 inches greater than the inseam.

As the confidence of riding a pedal bike increases, children would be able to drive without fear and with greater control.

What to Keep in Mind When Choosing a Bike Size?

Kids’ bikes should be ideally selected based on the current sizes of the children and not their future selves. This is because selecting a child kids’ bike larger than the one required may result in accidents and struggles that may cause the child to dislike the very notion of bikes themselves.

A bike is supposed to usher in a time of fun and adventure for young kids, and bikes of optimum sizes thus contribute to both the physical and mental development of children.

Keep in mind that seat height should be as low as possible in the beginning. As the child develops greater confidence, the seat post can be elevated higher.

Increasing seat post elevation reduces the instances of the feet touching the ground, which is a sign of greater confidence within the rider.

As you buy a bike, make sure to test ride it with the youngster on it to get an accurate idea of how the child´s body fits on the frame. There is nothing worse than selecting a bike without testing it and regretting it later once you’ve had a chance to inspect it at home.

Read Also: What Size Bike Do I Need? Bike Size Charts & Buying Tips


The quest to find the right bike for a kid has been a somewhat tricky ordeal due to a prevalent notion of using incorrect data to determine the size of the frame required.

However, as shown in this article, the process of bike sizing doesn’t have to be that hard. All you need to do is get the correct length of the inseam and use it to select a child´s bike that’s one size larger than the one on the chart.

A child´s first new bike is supposed to be a transformative experience for any youngster. It’s the first real vehicle that they’ll drive and thus, it’s essential for the accompanying adult to make sure that the bike is of the right wheel size.