Kids' bike size chart
Children’s bikes are sized by wheel, not frame. Height and inside leg tell you which wheel; age is the last thing to check.
Checked against UK retailer charts on 18 October 2026.
Size chart by height and inside leg
| Wheel size | Rider height | Inside leg |
|---|---|---|
| 12" | 85–98 cm | 33–41 cm |
| 14" | 88–104 cm | 36–51 cm |
| 16" | 95–114 cm | 41–51 cm |
| 20" | 114–129 cm | 53–63 cm |
| 24" | 128–143 cm | 57–68 cm |
| 26" | 135–150 cm | 61–81 cm |
Raleigh's inside-leg minimum is with the saddle at its lowest and the maximum is with it at its highest, so a child near the minimum has the most growing room.
Size chart by age
| Height | Inseam | Approx. age | Wheel |
|---|---|---|---|
| 86–102 cm | 15–18 in | 2–4 years | 12" |
| 99–117 cm | 16–22 in | 4–6 years | 16" |
| 114–132 cm | 19–25 in | 6–8 years | 20" |
| 130–150 cm | 23–28 in | 9–11 years | 24" |
| 146–160 cm | 25 and up in | 11–13 years | 26" or XS adult frame |
Trek says to start with height because "kids grow at different speeds". The age column overlaps for a reason: a tall 6 year old and a small 8 year old can both be on a 20".
How to measure inside leg
- Child stands barefoot or in socks with their back to a wall.
- Put a hardback book between their legs, spine up, and lift it gently until it's snug, like a saddle.
- Mark the top of the spine on the wall and measure from the floor in cm.
Cycling UK also suggests a quick cross-check: measure standing height and sitting height against a wall, and subtract. Its rule of thumb is that the wheel diameter in inches shouldn't be more than the inside leg in inches. A 41 cm (16 in) inside leg means 16" wheels at most.
Between two sizes?
Raleigh's rule of thumb is to go for the smaller wheel to build confidence. Cycling UK also flags crank length: overlong cranks make pedalling awkward and raise the saddle, so a smaller bike with the right cranks often fits better. If you can, take your child to a shop to try both.
Looking up a wheel size you've seen advertised? Try what age is a 16", 20" or 24" bike for. Under-fives: balance bike sizes.
Questions
What size bike for a 6 year old?
16" or 20" depending on height. Raleigh starts 20" at 114 cm tall.
What size bike for a 10 year old?
Usually 24". Trek lists 24" for 9–11 years and 130–150 cm tall.
Should I buy a bigger bike to grow into?
Not by much. A bike that is too big is harder to control. If between sizes, Raleigh recommends the smaller wheel.
Where these numbers come from
- Raleigh kids' bike size guide
- Trek Store UK kids' bike sizing guide
- Cycling UK: the right size bike for a child
Checked 18 October 2026. Brands change their charts, so always check the size guide of the shop you're buying from.