Your complete guide to kids bike sizing
Find the right size for your child — with clear advice on height, inside leg and confidence at every stage.
If you’d like a hand choosing the right size, our team are always happy to help — just use the chat icon on the page. For a wider overview of kids bikes by wheel size and riding stage, see our Kids Bike Guide .
Quick answer: what size bike does my child need?
Most kids bikes in the UK are sized by wheel size (12”, 14”, 16” and so on). Height is a great way to narrow it down quickly, but the most reliable measurement is inside leg (inseam), because it relates closely to stand-over height and saddle height.
Use the chart below to find the best starting point, then head to how to measure your child if you’re unsure.
Once you’ve confirmed the right wheel size, our Kids Bike Guide explains what changes as children progress — from balance bikes through to junior MTBs, road and hybrid bikes.
If you’d prefer to browse everything in one place, you can also shop our full range of kids bikes.
Kids bike size chart (wheel size, height and inside leg)
Use this as a general guide. Different brands and models can vary slightly, so if your child sits between sizes, it’s worth checking inside leg and thinking about confidence and riding experience.
Size guide note: Our chart is designed as a helpful starting point. Kids bike fit can vary between brands and models, so check the specific bike’s sizing details before you buy.
| Wheel size | Child height | Inside leg | Approx age |
|---|
| 12” | 85–100cm | 30–40cm | 2–4 |
| 14” | 95–110cm | 38–50cm | 3–5 |
| 16” | 100–115cm | 40–55cm | 4–6 |
| 18” | 105–120cm | 45–58cm | 5–7 |
| 20” | 110–130cm | 50–65cm | 6–8 |
| 24” | 125–150cm | 58–75cm | 8–11 |
| 26” | 135cm+ | 65cm+ | 10+ |
Shop Kids Bikes by Wheel Size
Once you’ve identified the right wheel size, you can browse bikes available in that size below.
12" kids bikes | 14" kids bikes | 16" kids bikes | 18" kids bikes | 20" kids bikes | 24" kids bikes | 26" kids bikes |
Taller young riders may also be ready for 27.5" junior bikes, which often suit riders moving toward adult mountain bike sizing.
Why kids bike sizing can vary between brands
Even if two bikes are the same wheel size (for example 20”), they can feel different because of frame geometry, stand-over height, tyre size, and how much saddle and bar adjustment is available.
- Lightweight / performance kids bikes often use more precise fit guidance (inside leg is especially useful).
- More upright “comfort” kids bikes can feel shorter and easier to manage at low speeds.
- MTB-style kids bikes may feel longer and more stable, but need the right stand-over for confidence.
If you’re also deciding between bike types and stages, our Kids Bike Guide breaks down the key differences by wheel size — and when it makes sense to move up.
Tip: age is only a rough guide. Two children of the same age can be different heights, and confidence plays a big part too.
Balance bikes vs pedal bikes: sizing differences
Balance bikes are usually sized by minimum saddle height, because the goal is for your child to sit comfortably with feet flat on the ground. If the saddle won’t go low enough, a balance bike can feel intimidating.
Pedal bikes still need a safe starting point, but saddle height and reach become more important as speeds increase — especially once you add gears. If your child is moving from a balance bike to pedals, choosing a bike that feels manageable (rather than “something they’ll grow into”) usually leads to a smoother transition.
Browse: kids balance bikes
FAQs
Here are the questions parents most often ask when choosing the right kids bike size.
What size bike for a 5-year-old?
Many 5-year-olds fit a 16” or 18” bike. Use height and inside leg as your main guide. Browse our 16 inch kids bikes and 18 inch kids bikes to compare options.
What size bike for a 7-year-old?
Many 7-year-olds move into a 20” bike. Smaller riders may still suit 18”, while taller or confident riders may be ready for 24”. Explore 20 inch kids bikes or 24 inch kids bikes.
What size bike for a 10-year-old?
Most 10-year-olds ride a 24” bike, but taller riders may be ready for 26”. See our 24 inch kids bikes and 26 inch kids bikes.
What size bike does my child need UK?
In the UK, kids bikes are sized by wheel size rather than frame size. Height and inside leg give the most accurate fit, so we recommend using both when choosing.
What age is a 20 inch bike for?
A 20” kids bike usually suits children aged around 5–8, but height and inside leg are more accurate. Browse 20 inch kids bikes to see current models.
What age is a 24 inch bike for?
A 24” bike typically suits ages 8–11, depending on height and confidence. View 24 inch kids bikes.
Is height or inside leg more important?
Inside leg is usually the most accurate way to size a kids bike because it helps ensure your child can stand over the bike safely and control it confidently. Height is still a useful starting point, but we recommend checking both.
How do I know if a bike is too big?
A bike may be too big if your child struggles to start and stop, can’t put a foot down comfortably, or feels stretched reaching the handlebars. A slightly smaller bike often helps build confidence faster.
Is a balance bike better than stabilisers?
Many parents and coaches find balance bikes help children learn faster because they develop balance and coordination from the start. Explore our kids balance bikes to see current options.
Should I buy a bike for my child to grow into?
A small amount of growth room is fine, but a bike that’s too big can make riding harder and reduce confidence. A well-fitting bike helps children learn faster and enjoy riding more.