Kids grow at wildly different rates. The number one mistake parents make when buying a bike? Shopping by age alone. A 6 year old on a bike sized for the average 6 year old might still be way off. This page matches your child to the right kids bike by wheel size and height, with options from 12 inch through to 24 inch. Know their age? Good start. Know their height or inseam? Even better.

Kids Bikes by Age

Age is a handy starting point, but it's just that, a starting point. Two children of the same age can need completely different bike sizes, so height and inseam are the measurements that matter most. Use these bands as a rough guide, then check against height and inseam before you commit.

Ages 2 to 4 (toddler cycle territory):

A 12 inch bike is usually the sweet spot for a first pedal bike. Training wheels do the heavy lifting here, and low seat heights mean little legs can plant firmly on the ground.

Ages 4 to 6:

A 14 inch or 16 inch bike suits most kids in this range. They're steadier on the pedals and often ready to ditch training wheels. If you're also sorting a birthday, have a look through toys for 3 to 5 year olds for milestone ideas.

Ages 6 to 8:

16 inch to 20 inch bikes. Kids at this stage want to keep up with their mates and can handle hand brakes.

Ages 9 and up:

A 20 inch or 24 inch bike, often with gears, for longer rides and hills.

Kids Bikes by Wheel Size (12" to 24")

Wheel size is the most reliable way to match a bike to your child, because it tracks height, not birthdays. Here's how the sizes shake out:

12 inch (30cm bike):

Toddlers and preschoolers around 85cm to 100cm tall. First pedal bike territory.

14 inch bike:

A useful in-between size for kids who've outgrown a 12 but aren't quite ready for a 16.

16 inch (40cm bike):

 Fits most 4 to 6 year olds, roughly 105cm to 120cm tall. Hand brakes start to make sense here.

18 inch bike:

 Another transitional size, sitting between a 16 and a 20.

20 inch (50cm bike):

Suits 6 to 9 year olds, usually 120cm to 135cm. Gears and geared BMX styles start showing up. Pair a 20 inch bike with toys for 6 to 8 year olds if you're planning a birthday.

24 inch bike:

 For older kids 130cm and up, with proper multi-speed setups for longer rides.

How to Measure Your Child for the Right Bike

Here's how a Toys R Us staff member would size your child up if you walked in with a tape measure.

1. Measure the inseam.

Shoes off, feet a few centimetres apart, standing against a wall. Pop a book firmly between their legs, spine up, like a bike seat. Mark where the top of the book meets the wall, then measure from the floor to the mark. That's their inseam. It's the single most useful number when picking a bike.

2. Check standover clearance.

When your child stands over the frame with both feet flat, you want around 2cm to 5cm of gap between them and the top tube. Any less and the bike's too big.

3. Check the seat height.

 For beginners, both feet should sit flat on the ground when they're on the seat. Confident riders can get away with tiptoes, which gives more efficient pedalling.

4. Sizing up.

 Don't jump a size hoping they'll grow into it. A too-big bike is hard to control and knocks confidence fast. Wait until they've properly outgrown the current size, then step up. For older kids moving into 24 inch territory, toys for 9 to 11 year olds has more age-appropriate picks alongside.

Training Wheels & First Pedal Bikes

Training wheels are a stepping stone, not a permanent fixture. Most of our 12 inch and 16 inch bikes come with training wheels included, so kids can build pedalling confidence without wobbling all over the driveway. Once they're steady on the pedals and steering without drama, usually within a few months, take the wheels off and let them find their balance. Every child gets there differently and in their own time. Some lose the training wheels after a weekend, others take a few months. 

If your child isn't ready for pedals yet, a balance bike is a smart start. On a first pedal bike, look for a lightweight frame they can pick up themselves, an adjustable seat that grows with them, and a simple coaster brake.

Shop Kids Bikes at Toys R Us Australia

Every bike in this range ships across Australia, with click-and-collect at selected stores. Once you've locked in the right size, pair it with kids helmets and accessories so they're set up safely from day one. Want to see scooters and trikes too? Browse the full bikes and riding range.

Kids Bike Sizing FAQs

What size bike does a 3 year old need?


Most 3 year olds fit a 12 inch bike with training wheels. Check the inseam is at least around 35cm to 40cm so they can plant both feet on the ground while seated.

What size bike for a 4 year old?


A 14 inch or 16 inch bike suits most 4 year olds, depending on height. If they're tall for their age or already confident on a 12, go straight to a 16.

How do I know if the bike is too big?


If your child can't touch the ground with the balls of their feet while seated, or there's no clearance between them and the top tube when standing over the frame, the bike's too big. Size down.

Should I get training wheels or a balance bike?


Under 3s and nervous starters usually do better on a balance bike, which teaches steering and balance first. Kids 3 and up who are already confident often go straight to a pedal bike with training wheels.

When can kids move to a 24 inch bike?


Usually from around age 9, or once they're 130cm tall and have comfortably outgrown a 20 inch. Look for gears at this size for longer rides.