Kids' Bike Size Guide: What Size Bike Does My Child Need?
"What size bike does my child need?" is the question we're asked most — and the honest answer is: don't buy on age alone. Two children the same age can be a head apart in height. The reliable way to size a kids' bike is by wheel size, matched to your child's height and inside-leg. Here's how to get it right first time.
Why kids' bikes are measured in wheel size
Unlike adult bikes (measured by frame), children's bikes are sized by their wheel diameter — 12", 14", 16", 20", 24" and 26". As the wheel grows, so does the whole frame. Getting this right matters: too big and your child can't control it or put a foot down; too small and they're cramped and pedalling inefficiently.
Kids' bike size chart by age, height & inside-leg
Use this as your starting point, then confirm with the inside-leg measurement below. Ages overlap on purpose — height is the better guide.
| Wheel size | Approx age | Child height | Inside leg | Bike type |
|---|---|---|---|---|
| 12" balance | 18 months–3 yrs | 85–100 cm | 30–42 cm | Balance bike |
| 16" | 4–6 yrs | 105–120 cm | 45–55 cm | First pedal / hybrid |
| 20" | 6–8 yrs | 120–135 cm | 55–63 cm | Hybrid / mountain |
| 24" | 8–11 yrs | 135–150 cm | 63–72 cm | Hybrid / mountain |
| 26" | 10–14 yrs | 145 cm+ | 70 cm+ | Hybrid / mountain |
Between two sizes? If your child is confident, size up for longer use. If they're cautious or just starting out, the smaller wheel gives more control.
How to measure your child's inside leg
This is the number that really matters — it tells you whether your child can stand safely over the bike and reach the ground.
- Stand your child against a wall, barefoot or in socks, feet slightly apart.
- Pop a book between their legs, spine up, snug against the body like a saddle.
- Measure from the top of the book to the floor in centimetres.
That inside-leg figure should sit within (or just above) the bike's standover range, so they can plant both feet when stopping.
Matching your child to a Shyre
- 12" — the 2.9kg Myndie balance bike, for first wobbles from 18 months.
- 16" — the Hopton 16", a light first pedal bike for roughly 4–6 years.
- 20" — Hopton or Eastie 20", hybrid or mountain, for around 6–8 years.
- 24" — Hopton or Eastie 24", geared, for roughly 8–11 years.
- 26" — Hopton or Eastie 26", for older children up to 14.
Prefer to skip the maths? Our bike size finder takes your child's inside-leg and points you straight to the right size in seconds.
Should I size up so the bike lasts longer?
It's tempting, but a bike that's too big is harder to control and less fun — which can put a child off riding altogether. Buy the size that fits now, and when they outgrow it, our trade-up scheme puts credit towards the next size while the old bike rolls on to another family. Right size, less waste.
Still not sure?
We're a real family in Shropshire and we're happy to help you choose. Drop us a message with your child's age and inside-leg and we'll point you to the perfect fit.
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