The kids' bike sizing guide below will give you an overview of the various kids bike sizes, and show you how to choose the right size bike for your child based on leg length and rider experience rather than the ineffective method of age and wheel size.
What, how can this be? This is because the same size bike can have very different geometries, especially when you find brands like Guardian Bikes that design bikes specifically for kids.
When purchasing a kids bike, you should never choose a bike size based on an age range that is listed on a sizing chart. There are 2 main reasons for this:
Bike sizing is the most important aspect to get right when deciding on a bike for your child. If the bike is too big or too small, it can ruin your child's biking experience and lead to accidents.
Kids bikes come in these different sizes which are based on the wheel size of the bike: 12 inch, 14 inch, 16 inch, 18 inch, 20 inch, 24 inch, and now even 26 inch. The wheel size is based on the diameter of the tire (see below) and as each tire size gets larger, so does the size of the bicycle frame. These different wheel and frame sizes help companies design bicycles that will fit kids of all ages. The most common sizes are: 12 inch, 14 inch, 16 inch, 20 inch, and 24 inch. You will learn later on why wheel size is NOT the best way to choose a bicycle for your child.
If you have ever purchased a bike before, you have probably seen a chart like the one below. These charts are designed for you to use your child's height to determine the correct wheel size. Sounds simple right? Then you finally get into the store, sit your child on a few bikes with the correct wheel size, only to realize that the bikes seem to fit differently.
The main problem is the size of the bike is not solely determined by the wheel size of the bike. The size of the frame and design of the geometry also matter. This is why the same company can have two 20 inches bikes that are designed to fit children of completely different heights. An example of this is illustrated below when comparing Guardian’s 20 inch small vs 20 inch large kids bike sizes.
Figure 1: 20 Inch Small Bike
Figure 2: 20 Inch Large Bike
Figure 1: 20 Inch Small Bike
Figure 2: 20 Inch Large Bike
Notice how both bikes have 20 inch wheels but the bike in figure 1 has a shorter wheelbase and lower seat position. This bike has been specifically designed for a smaller kid. There are more extreme examples if you begin to compare two bikes from different brands where the minimum seat height of two bikes with the same wheel size can vary up to 5 inches!
Another issue with this method is the difficulty in trying to figure out which bike is going to last the longest and how long the bike is going to last.
The most accurate way to find the right kids bike size for your child is to look at their bike leg length measurement and experience and compare it with the seat height of the bike. To make this easier, lets define each of these terms.
Bike Leg Length = measured from the top of the crotch to where your child’s feet touch the ground (with shoes on!).
Note - bike leg length is different than pant leg length.
Rider Experience = some questions include: have they ridden a bike before? Did they start on a balance bike? Are they timid or confident?
Seat height = this is the range of how low and how high the seat will go on a bike. For example, our Guardian 16 inch bike has a seat height range of 18.5 – 23.5 in
Here is an easy step-by-step guide for measuring your child’s leg length:
1
Have them stand up straight against a wall with their feet shoulder width apart and their shoes on.
2
If you want to ensure your measurement is as accurate as possible, you can place a book (hardbound) between their legs and to the top of the crotch area.
3
Measure from the ground to the top of the book (to their crotch) to get their bike leg length.
Now that you have measured their leg length, the next step is to understand their riding experience.
If your child is under the age of 4 and has not ridden a balance bike or pedal bike before, we strongly recommend you take a look at starting them off on a balance bike. You can learn more about balance bikes at the bottom of this page.
This will be my child’s first pedal bike & did NOT use a balance bike Created with Lunacy Created with Lunacy
If this is your child’s first pedal bike and they didn’t use a balance bike, then their feet should be flat on the ground when sitting on the seat. By teaching your child to balance first rather than with trainining wheels, your child will learn much faster and be riding on their own before you know it.
This will be my child’s first pedal bike & did use a balance bike Created with Lunacy Created with Lunacy
Timid Riders
If this is your child’s first pedal bike and they used a balance bike, then their feet should be flat on the ground when sitting on the seat.
Confident Riders
If this is your child’s first pedal bike and they used a balance bike, then their heels can be up to 2 inches off the ground when sitting on the seat.
This will be my child’s second (+) pedal bike Created with Lunacy Created with Lunacy
If your child has already ridden a bike without training wheels, then they should be riding with their heels 2-3 inches off the ground while sitting on the seat. This is great news for you as a parent because your child will get more life out of the bike than kids who currently have less experience. With their heels 2-3 inches off the ground and the seat set higher, your child will have proper leg extension for maximum pedaling efficiency.
Now that you have measured their leg length and looked at their experience, the final step is to match that up against the seat height of a bike.
As parents, we like to purchase things (or items) for our kids that will last. When it comes to a kids bike, you will always want to get your kid on a bike towards the minimum seat height so that the bike has room to grow.
Minimum seat height = Inseam + heels off the ground (see above on experience)
I.E. a new rider with an leg length of 18 inches
Now that you know their minimum seat height, you can start shopping around!
Want to make it easy on yourself? Use our RideSizer® tool below. Please note this only works for Guardian Kids Bikes.
When you go to purchase your child’s first bike, you will have two options: training wheels or balance bike. What’s the difference? We will break it down for you:
Training Wheels: An add-on part that can be attached to a two-wheeled bike. For a lot of parents, this is how you learned to ride a bike. Training wheels sound like a great deal because the child can learn to ride with the training wheels on and when the time comes to pop the training wheels off, you have a regular bike. The downside of training wheels is that it could take the child longer to learn to balance if they are relying on those extra wheels to hold them up.
Balance Bikes: With only two wheels and no pedals, these bikes require the child to sit on the saddle, scoot, and balance. Many resources say balance is the hardest part of learning to ride, so transferring to a pedal bike is easier for children that start out on a balance bike.
Ultimately, the choice is up to you and your family. Your local bike shop can also help you make the right decision for your child.