Buying the right size is the single biggest factor in whether your child actually rides. Too big "to grow into" makes starting and balancing scary; too small gets outgrown fast. Use the calculator below — enter your child's age, height, or (best of all) inside-leg measurement — for the right wheel size and the closest Gear Force bike.
Kids Bike Size Calculator
Find the right wheel size by your child's measurements — inseam (inside leg) is the most accurate, so use it if you can.
Free tool by Gear Force — kids' bikes, balance bikes & ride-ons, Australia-wide.
Kids bike size chart (by age, height & wheel size)
| Wheel | Age | Height | Inside leg |
|---|---|---|---|
| 12" (balance) | 2–4 | 85–100 cm | 30–42 cm |
| 14" | 3–5 | 95–110 cm | 40–50 cm |
| 16" | 4–6 | 105–120 cm | 45–55 cm |
| 18" | 5–7 | 115–128 cm | 55–63 cm |
| 20" | 6–9 | 122–140 cm | 60–74 cm |
| 24" | 8–11 | 135–155 cm | 72–86 cm |
Age is a starting point — height and especially inside-leg give a better fit. When between sizes, size down for confidence.
How to measure inside leg
Stand your child barefoot against a wall, pop a book up between their legs (spine up, like a saddle) and measure from the top of the book to the floor in cm. That number is the best predictor of the right bike.
FAQ
What size bike for a 5 year old? Most suit a 16" bike, but check height/inside-leg — taller kids may already fit an 18–20".
Should I buy bigger to grow into? No — an oversized bike is harder to control. Buy to fit now.
Balance bike or pedal bike first? Under ~4, a balance bike teaches balance fastest. See our Balance Bike Readiness Checker.
Ready to pick the bike?
Shop all Kids Bikes →
Shop Balance Bikes (first riders) →
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<p>Powered by the <a href="https://gearforce.com.au/blogs/kids-bikes/kids-bike-size-calculator">Kids Bike Size Calculator</a> from <a href="https://gearforce.com.au/">Gear Force</a>.</p>More free Gear Force tools
- Kids Bike Size Calculator
- Balance Bike Readiness Checker
- Hoverboard Suitability Checker
- Kids Ride-On Car Selector
- Kids Helmet Size Finder + Learn to Ride
Gear Force is an Australian specialist in kids' bikes, balance bikes, ride-on cars and hoverboards, shipping nationwide from Melbourne. Our guidance is based on the geometry of the products we actually stock and years of helping families fit first-time riders.
