What Size Bike for a 4 Year Old: A Helpful Guide for Parents

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If you’re at all confused about what size bike for a 4 year old do you need to buy, then you certainly aren’t alone. It can be tricky knowing what to go for and especially because there are so many brands, sizes, and styles available.

Factors to Consider When Buying a Kid's Bike

Deciding upon that new two-wheeled Christmas or Birthday present for your four-year-old kid can be overwhelming. You want to deliver the real wow factor, but you’re worried about getting the frame and wheel size incorrectly. You want something that’s going to last for a few years, and they won’t automatically outgrow.

Apart from that, you want to ensure that it’s safe and they can use it straight away rather than having to wait a few months. There’s nothing more frustrating than seeing a shiny new bike in the garden and not being able to get on board and go for a ride! Bikes are undeniably one of the best gifts that money can buy, so it’s vital that you get it right.

Why It's Important to Get Your Child on a Bike

Bikes are liberating. They bring a whole new found sense of freedom and fun. It can also be a fantastic way for your child to get around and begin exploring their immediate environment even if the initial exploration is within your backyard.

Getting a kid to be physically active and encouraging them to spend some valuable time away from a screen or games console can be challenging but is definitely rewarding.

Bikes are also a great way for family members of all ages to bond and spend valuable time together. That might be a real Sunday afternoon bike ride after the typical family meal or even participating together in a car-free commute to school.

Why You Need to Get the Right Size of a Bike

Getting the right sized bike isn’t just a matter of comfort; it’s also about safety. Yes, kids grow fast. Some faster than others and you might be frustrated by the regularity with which you seem always to be buying new shoes and clothes.

Thankfully, when it comes to more significant purchases like bikes, they are, for the most part, adjustable and designed to grow with your kids. Handlebars and saddles can usually be height adjusted, and wheel sizes are interchangeable.

However, you will need to buy the best fitting bike frame. That said, while with adult bikes, it’s all about the frame size, with kids' bikes, the wheel diameter is the critical measurement to take into consideration.

If you are at all confused, you can always go into a local bike store and ask for their expert advice. You might even take your enthusiastic four-year-old along with you and get them to try out what fits.

Let them have a short cycle around the showroom, and they’ll soon let you know what they like. You will instantly get a register on whether the bike is indeed the right size or not.

If it’s a big surprise that you’re trying to keep a secret until Christmas, then that’s where a handy guide on the best ways to size up a kid's bike comes in.

What Size Bike for a 4 Year Old Is Best

Assuming that you do want to keep the purchase of what might be their very first set of wheels a total secret, then you’re going to need to measure the height of your four-year-old before you do anything. That should be easy enough to do without arousing any suspicion. After all, we were probably all regularly measured against our siblings for at least the first fifteen years of our life!

With kids' bikes, the crucial consideration as we just mentioned is the wheel diameter. Most manufacturers will have size charts that you can refer to which include the wheel size, age of the child in years, and the height of your child. You may have a particularly tall four-year-old at home, in which case, you might need to go for a 14-inch as opposed to a 12-inch wheel.

As a guide, you can use this handy chart put together by a popular bike company called Halfords.

Measuring Your Child for Their New Bike

The most common sized wheel diameters for kids are 12”, 14”, 16”, going all the way up to 20”. For most average sized four-year-olds, though, the 14” is going to be the optimal one. Still, it is best to measure your kid to make sure that you are purchasing the best size.

To accurately measure up your child, you are going to need to take an inseam measurement. The best way to do this is to have your child stand barefoot with their back against a straight wall then place a mark with a pencil at the top of the inner leg, close to the crotch.

Next, take your tape measure and measure the distance from the pencil mark down to the floor. This is important as you want your child to be able to place their feet securely on the ground, especially when they are first learning to ride. They’re likely to be less unsteady and frequently need to stop, especially when they first take off those stabilizers. As such, the kid being able to put their feet flat on the ground will instill a greater sense of confidence.

Other Considerations

The bike or wheel size is not the only thing to keep in mind when purchasing a bike for your kid, as well as when they start riding it.


This is an important consideration too. The handlebars also need to be at the correct height to be safe and comfortable for your four-year-old. With the right handlebars, they can hit the brake quickly and easily, as well as sit in a relaxed and natural cycling position rather than being too hunched over.


The most important consideration is always safety, no matter what age your child is. Helmets are essential, as are closed toed shoes and tightly fastened laces. Some four-year-olds may even benefit from having a balance bike, especially if this is the first bike that you’ve actually bought for them.

Balance bikes are designed for kids from ages three through to five and can be a great way for your child to build up initial confidence before they venture onto a pair of pedals.

How do you determine bike size for a child?

There are a few ways to determine the appropriate bike size for a child:

Use the child's height as a guide

Most bike manufacturers provide a size chart that lists the appropriate bike size based on the child's height. This is a good starting point, but it is not always accurate.

Measure the child's inseam

This is the distance from the child's crotch to the ground. This measurement can be used to determine the appropriate size of the bike's seat tube.

Check the standover height

This is the distance from the ground to the top tube of the bike when the bike is standing upright. The child should be able to stand over the top tube with both feet flat on the ground.

Test ride the bike

Once you have a general idea of the appropriate bike size, have the child test ride the bike to ensure that it is comfortable and easy to control.

Consult the experts

If you're still uncertain, it's best to take the child to a bike shop for expert fitting. The bike shop staff will be able to determine the appropriate bike size based on the child's height, inseam, and riding experience.

It's important to keep in mind that as the child grows, they may need to move up to a larger size bike. Therefore, it's important to choose a bike with adjustable seat post and handlebar stem to accommodate the child's growth.


Generally speaking, a 12” or 14” wheel diameter should be fine. Nonetheless, it’s always best to measure your child and refer to the manufacturer sizing guidelines before you go ahead and make that exciting first investment in a new kid's bike.

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