How To Size A Mountain Bike For A Kid? (Pick The Right One)

There is no secret that kids love bikes! As soon as they can get on one which usually happens between one and two years old they simply won’t get off.

But it is your job as a parent to make sure they get a safe bike for their age. It might sound easy but it is not always like that. Even if most mountain bike manufacturers offer different models and sizes of bikes for different age group, your child might not follow that pattern.

Children grow at different rates and what is recommended for an average child, might not be the perfect match for your child. If you find yourself in this situation, here’s the best guide to use before buying a bike for your kid!

How to decide what size is the best size?

There are two aspects to consider when you buy the best mountain bike for your child: the size of the bike and the size of your child. When it comes to the size of the bike, the general rule says that your child should be able to touch the ground with their feet while they are on the bike. This trick will show you fast if a certain bike is good for them or not. But if you can’t actually get your child to try a bike in order to see if it fits them, you can go by the age sizes recommended by the manufacturer.

Bike size goes by the child’s age and their height. If you have these two characteristics figured out, you should be able to pick the best bike for them even without having them try it on first. The size of a bike is basically the size of the wheel’s diameter since the rest can be readjusted if needed.

And as a parent, you should have no problem knowing the child’s age and height so, you are all set to make the best decision! Here are the most useful bike sizes for different ages and heights to consider:

[accordion id=”my-accordion”]
[accordion_item title=”1-4 Year Old” parent_id=”my-accordion” open=”true”]
Height: 28 – 38 inches
Wheel diameter: 12 inches
[accordion_item title=”3-7 Year Old” parent_id=”my-accordion”]
Height: 38 – 48 inches
Wheel diameter: 16 inches
[accordion_item title=”5-9 Year Old” parent_id=”my-accordion”]
Height: 42 – 52 inches
Wheel diameter: 18 inches
[accordion_item title=”7-13 Year Old” parent_id=”my-accordion”]
Height: 48 – 60 inches
Wheel diameter: 20 inches
[accordion_item title=”10-15 Year Old” parent_id=”my-accordion”]
Height: 56 – 66 inches
Wheel diameter: 24 inches

As you can see these measurements are not exact and they definitely aren’t scientific. But it should give you a more accurate representation when you are shopping online for a mountain bike for your kid.

You also have to take into consideration that your child might be taller or shorter than others in the same age box. If this is the case, purchase the bike that suits their height rather than their age.

The temptation to try an adult bike as a pre-teen

Most pre-teens and teens have the temptation to upgrade to an adult bike, which means a 26 inches wheel size. But as a parent, you should put their safety first and try to avoid taking any unnecessary risks.

A 26 inches mountain bike will most likely be too big for a 10 years old child and even for a 13 years old one. This will put them in the hazard of losing control of the bike in the most dangerous moments during riding. And it takes just one mistake to get injured or even risk a tragedy! For safety reasons, you should consider getting your pre-teen or teen child a bike that is 24 inches and stick with it until they are tall enough to upgrade to a bigger one.

However, there are also children that grow taller than others. This is why knowing your child’s height is very important when choosing their mountain bike. If your child is tall enough, you can consider having them try a small adult mountain bike with 700 mm or 26-inch wheels. These bikes have a smaller frame than regular adult mountain bikes, even if the wheels are full size. But keep in mind that this is not an option for all children, especially during the pre-teen phase!

The dangers of getting the wrong mountain bike size

If you are not convinced yet when it comes to how important the size of the mountain bike actually is for your child, here are some potential risks that you might want to consider if you are purchasing the wrong bike for them!

  • They might not be able to control it and risk to fall easily which can be quite dangerous
  • It might be too heavy which means your child might find it very hard to ride it if they even decide to get on it at all
  • Also, if the bike is too small for them, they might develop severe back pain as they are trying to reach for the handlebars. This happens usually because the handlebars are too low on a smaller bike which makes them harder to reach
  • A wrong size bike will simply not “feel” right for your child and they might not enjoy riding as much as they would if the bike would be the good size for them

Common mistakes made by parents who are shopping for the best mountain bike for their kids

As a parent, you might be too enthusiastic to surprise your little one with the best mountain bike for them and make certain mistakes without even realizing. In order to not fall into such trap here are the most common mistakes to watch out for!

1. Don’t buy a bike that is bigger just so it will fit them later

This logic is very common and even if it might apply to other items like certain clothes, it is not a good idea when it comes to bikes. Many parents purchase clothes that will still fit the child next year and there is nothing wrong with that.

But when it comes to bikes, making the wrong decision could be life-threatening for your child. A bike is not a long-term investment, at least not when your baby is really young. When they are close to the teen phase, you can start thinking more long term but when they are 5 years old, they need a bike that fits them in the present!

2. Don’t try to adjust a bike that is too big or too small for your child

If you think about it, the most important feature of a bike is the size of the wheel, at least in terms of safety. And this is something that you can’t adjust at all, no matter how inventive you might be. You can adjust the sit or the handlebars but even this can be hard to do on certain bikes. Overall, trying to make a bike that is the wrong size fit your child, can be a significant waste of time and money!

3. Don’t just buy a bike because it’s cute

While this aspect of a bike should be important, it should never be the most important one! Your child might fall in love with a certain type of mountain bike maybe because its colors or features, but if you can’t find the right size for them, don’t invest in it. No matter how much they like it, chances are that they will not really use it if it is the wrong size. And you will end up wasting your money on a whim that you will regret soon!


Now that you are well aware of the best ways to get the right mountain bike size for your child, all you have to do is shop away! The market offers a lot of options and there is a bike for everyone! Remember the risks of purchasing a wrong size bike for your child. When it comes to their safety and health, no compromises should be made!

The best way to find the perfect mountain bike for your child is still to take them to a store and have them try several bikes. So, if you have the possibility to do that, by all means, go for it! Once you buy the right mountain bike for your child, you can be rest assured that they will have fun riding in the safest way possible!


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