Fitting a Kid for a Push Bike

Getting your kid properly fitted for a push bike isn't complicated, but it does require a few key measurements and a bit of observation. Whether you're surprising them with a new bike for Christmas or just replacing one they've outgrown, knowing how to size them up correctly makes all the difference between a bike they'll love riding and one that ends up gathering dust in the shed.

At On Two Wheels, we fit kids for bicycles every week, and the process is straightforward once you know what to look for. Here's what you actually need to measure and why it matters.

Why Proper Fitting Matters

A bike that's too big is genuinely unsafe. Kids can't reach the ground properly, can't control the brakes effectively, and lose confidence quickly. A bike that's too small is just frustrating and uncomfortable, and they'll outgrow it in months anyway.

The right size kids' bike means your child can touch the ground with both feet while sitting on the seat, reach the handlebars comfortably, and actually enjoy riding. Getting the perfect fit helps kids gain confidence, makes riding fun, and is the difference between a bike that gets ridden every weekend and one that sits in the garage untouched.

The Key Measurements You Need

 

You don't need special equipment or a formal fitting session to get accurate measurements. Here's what matters most and how to get the numbers.

Inseam Length: The Most Important Number

Inseam is the measurement from the ground to your child's crotch, and it's the single most important number for bike sizing. The child's inseam determines standover height and whether they can safely reach the ground when stopped.

How to Measure It

The easiest way is to have your child stand against a wall in their shoes, feet shoulder-width apart. Take a hardcover book and slide it up between their legs until it sits snugly (like a bike seat would). Mark where the top of the book hits the wall, then measure from the floor to that mark. This gives you an accurate fit measurement.

If you're trying to keep it casual (maybe it's a surprise gift), you can estimate it during regular activities. When they're getting changed, standing at a doorframe, or during one of those spontaneous height checks kids love, you can mentally note where their inseam sits and measure it later. If you know the width of your own hand, you can even use hand spans as a measuring unit and convert it to centimetres later.

For most kids aged 5 to 10, inseam measurements typically range from about 45cm to 65cm. This translates roughly to bike wheel sizes between 16 inches and 24 inches.

Height: The Supporting Measurement

While inseam is the star of the show, height gives you a useful double check. Most bike size charts list both height and inseam ranges, so having both numbers gives you confidence you're choosing correctly. Sizes based on height alone can be misleading, which is why inseam matters more.

You probably already know roughly how tall your child is, but if you want to be precise, a quick measurement against a wall does the job.

Reach and Proportions

Some kids are all legs, others have longer torsos. If you've noticed your child struggles to reach things or seems particularly long or short in the body compared to their height, make a mental note. Frame size affects their ability to reach the handlebars and the overall fit of their bike.

Watch how they sit at the dinner table or in the car. Can they comfortably reach forward? Do they tend to hunch or stretch? These observations help, particularly if you're choosing between two sizes.

Converting Measurements to Bike Sizes

Kids' bikes are sized by wheel diameter in inches, and it's not as straightforward as adult bike sizing. Here's how your measurements translate to actual bike sizes.

16 Inch Wheels

Typically suits kids with an inseam of 45cm to 55cm, roughly 100cm to 120cm tall. This is usually the first bike after a balance bike for most 4 to 6-year-olds. Young riders at this stage might still need training wheels while they build their balance and coordination.

20 Inch Wheels

The sweet spot for many primary school kids. A bike with 20-inch wheels suits inseams from 50cm to 60cm and heights between 115cm and 135cm. Most 6 to 9-year-olds ride 20-inch bikes. This size range covers everything from BMX bikes for tricks and jumps to mountain bikes for trail riding, depending on your little rider's interests and skill level.

24 Inch Wheels

For older kids or taller primary school students, typically those with inseams ranging from 58cm to 68cm and heights between 130cm and 150cm. This often covers ages 8 to 12, though every child grows differently. At this size, you'll find proper mountain bikes and road bikes designed for experienced riders who are ready for more serious riding.

These ranges overlap deliberately because kids grow at different rates and have different proportions. If your child is between sizes, consider their coordination and confidence. A cautious beginner does better starting smaller, while a confident rider can handle sizing up slightly. The right bike size depends on ability as much as measurements.

Checking the Fit

Once you've narrowed down the right wheel size, here's how to verify the bike actually fits properly. Getting the best fit means checking several key contact points.

Standover Height

When your child stands over the bike with both feet flat on the ground, there should be 2 to 5cm of clearance between the top tube and their crotch. This ensures they can safely dismount and won't hurt themselves if they slip off the seat.

Seat Height

When seated with the pedal at its lowest point, your child's leg should be slightly bent at the knee. They shouldn't be fully stretched out, but they also shouldn't be cramped. Proper leg extension means efficient pedalling and comfortable riding.

They should also be able to touch the ground with the balls of their feet while seated (or flat-footed for very young or nervous riders). This gives them confidence and control when stopping.

Handlebar Reach

Your child should be able to reach the handlebars comfortably without stretching or hunching. Their elbows should have a slight bend, and they should be able to easily reach and operate the brakes.

What About Helmets and Other Gear?

While you're sorting out bike sizing, you'll want to get a helmet sorted too. Helmet sizing is based on head circumference measured about 2cm above the eyebrows.

For a casual measurement, when you're brushing their hair or they're sitting on your lap, wrap a soft tape measure (or a piece of string you measure later) around their head. You can make it playful so they don't question it.

Most kids aged 5 to 10 need bike helmets sized between 50cm and 56cm. Helmets should fit snugly but not squeeze, and the fit can be fine-tuned with the adjustment dial at the back.

Using Their Current Bike as a Reference

If they already have a bike (even if it's too small), take a good look at how they sit on it. Are their knees hitting the handlebars when they pedal? That's a clear sign they need a bigger bike. Can they touch the ground flat-footed while seated? If not, the current bike is probably too big, so don't go up another size yet.

Take a photo of them on their current bike from the side. You can show this to staff at a bike shop, and they'll be able to advise on sizing up appropriately.

When You're Still Not Sure

Getting kids' bike sizing right doesn't have to be perfect science, but if you're genuinely unsure or stuck between two sizes, we can talk you through it. We've sized up hundreds of Sydney kids over the years and can help you make the right call based on your measurements.

You don't need to bring your child in to get good advice. Just bring your measurements (and that photo if you have one), tell us about their riding ability and confidence level, and we can point you to the right options from our range of kids' bikes.

The beauty of buying from a local shop rather than online is that if you get it home and the sizing isn't quite right, you can actually do something about it. We'd much rather help you get it perfect than have a disappointed kid stuck with the wrong size. If you can bring them in, a proper test ride is always the best way to confirm you've found the perfect bike.

Making It Happen

If you're planning a surprise (Christmas is coming up, after all), you've got options for keeping it secret. You can shop online and have it delivered to work or a friend's place. You can visit our Gledswood Hills shop during school hours. You can send your partner or a grandparent with your measurements and specifications.

If you're buying in person, we can help you load it discreetly into the car. We've been helping parents pull off surprise bike gifts for years.

But even if it's not a surprise, the same measurements and fitting principles apply. Bringing your child in for a proper fitting is always an option, and sometimes it's the best way to ensure you get it exactly right, especially for kids who are between sizes or have specific needs. Watching them on a pedal bike in person helps us determine the perfect size bike for their build and abilities.

Get It Right with On Two Wheels

Those few minutes of measuring and observation mean your child gets a bike they can actually ride confidently and safely. Whether it's a Christmas surprise or just time for an upgrade, proper fitting makes all the difference.

If you're still working out the details or want to see what's available in the right size, drop into On Two Wheels at Gledswood Hills or explore our range of kids' bikes online. We're always happy to help Sydney parents get their kids fitted properly for a push bike.