Enter your child's height for an instant wheel size recommendation — height beats age every time.
6 yrs
Bike type
Please enter a valid height between 70 cm and 175 cm.
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Recommended wheel size
20"
wheels
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About this Australian bike size tool
Finding the right bike for an Australian child is straightforward once you use height instead of age.
Wheel diameter — measured in inches — is the key spec: a 20″ wheel bike suits most children
between 115 cm and 135 cm regardless of whether they're 6 or 9 years old. This calculator
uses Australian retail sizing conventions and metric measurements throughout. Unlike many overseas
guides, it covers the full range of bikes available in Australian shops — from 12″ balance bikes
through to 26″ junior mountain bikes — and flags when your child's inseam-to-height ratio
suggests they could size up. Always confirm fit in-store by checking your child can comfortably
reach the ground while seated.
Full Australian kids bike size chart
Wheel Size
Height (cm)
Typical Age
Frame Size
Best For
12″
85–100 cm
2–4 years
XS
Balance bikes, first pedal bikes
14″
95–108 cm
3–5 years
XS
First pedal bikes
16″
100–117 cm
4–6 years
S
Kids pedal bikes
18″
110–122 cm
5–7 years
S
Transitional size
20″
115–135 cm
6–9 years
M
Most popular kids size — junior MTB entry
24″
130–150 cm
8–12 years
L
Older kids, junior mountain bikes
26″
145–170 cm
11–14 years
XL
Junior/adult crossover
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Frequently asked questions
In Australia, kids' bikes are sized by wheel diameter in inches. The right size depends primarily on your child's height in centimetres, not their age. As a general guide: children around 100–115 cm typically suit a 16″ wheel; 115–135 cm suits a 20″ wheel; and 130–150 cm suits a 24″ wheel. Always confirm the fit in-store by checking that your child can touch the ground comfortably with both feet while seated.
Height is significantly more reliable than age for bike sizing. Children of the same age can vary by 15 cm or more in height — which can mean a full wheel size difference. Age ranges in size charts are a rough starting point only. Always measure your child's actual height and use that as the primary input. Adding inseam length gives you an extra layer of accuracy for checking frame fit and standover height.
Have your child stand straight against a wall in their shoes, feet about 15 cm apart. Hold a book flat between their legs (spine up) and press it gently to their crotch. Measure from the floor straight up to the book's spine — that's the inseam. This length should be equal to or slightly greater than the bike's minimum seat height. A 5–10 cm gap between inseam and the lowest seat position is comfortable for most kids.
No — buying a bike that is too large is one of the most common mistakes Australian parents make. A child who cannot comfortably reach the ground or control the bike is at greater risk of falls and may develop poor riding habits that stick. The correct fit allows them to touch the ground with feet flat while seated. If your child is near the upper end of a size range, sizing up by half a step is reasonable; going a full wheel size up is generally not recommended.
For most Australian 5-year-olds, a 16″ wheel bike is the most common fit. However, this depends entirely on height, not age. A tall 5-year-old at 115 cm or above may suit a 20″ bike, while a smaller child around 100 cm may still be on a 14″ or 16″. Measure your child's height and use the calculator above for an accurate recommendation — their birthday is the least useful piece of information when it comes to bike sizing.