Kids bike size chart by age and height
That first wobbly ride is a big deal. A bike that fits makes it a happy one.
Short answer: kids' bikes are sized by wheel size (12 to 26 in), not frame size. Use your child's height and inseam; age is only a rough guide because kids grow at different rates.[1 · Oct 23, 2026; 2 3 · Oct 29, 2026]
Published charts side by side
| Wheel | REI: height / inseam / age[1 · Oct 23, 2026] | Trek: height / inseam / age[2 · Oct 29, 2026] | BikeRadar: minimum height / inseam[3 · Oct 29, 2026] |
|---|---|---|---|
| 12 in | 2'10"–3'4" / 14–17 in / 2–3 | 3'0"–3'3" / 15–18 in / 2–3 | 2'8" / 12 in (often a balance bike) |
| 14 in | 3'1"–3'7" / 16–20 in / 3–4 | not listed | 3'3" / 15 in |
| 16 in | 3'7"–4'0" / 18–22 in / 4–6 | 3'5"–4'0" / 16–22 in / 4–6 | 3'5" / 16 in |
| 18 in | not listed | not listed | 3'8" / 18 in |
| 20 in | 4'0"–4'5" / 22–25 in / 5–8 | 3'9"–4'6" / 19–25 in / 5–8 | 3'11" / 20 in |
| 24 in | 4'5"–4'9" / 24–28 in / 7–11 | 4'1"–4'11" / 23–28 in / 8–11 | 4'2" / 23 in |
| 26 in | 4'9"+ / 28 in+ / 10+ | 4'8"+ / 25 in+ / 10–12 | 4'7" / 25 in |
Quick lookup by height
Our own summary of where the three charts above agree or overlap:
| Child's height | Wheel size to try first |
|---|---|
| under about 3'1" | 12 in (or a balance bike) |
| about 3'1" to 3'5" | 12 or 14 in |
| about 3'5" to 4'0" | 16 in |
| about 4'0" to 4'5" | 20 in |
| about 4'5" to 4'9" | 24 in |
| about 4'8" and up | 26 in, or the smallest adult frame |
Charts overlap at the edges and the same wheel size fits differently between brands, so check the maker's own chart and have your child try the bike.[1 · Oct 23, 2026; 2 · Oct 29, 2026]
How to measure inseam
- Have your child stand against a wall in socks.
- Slide a hardcover book, spine up, snugly between their legs.
- Mark the wall at the top of the spine and measure from the mark to the floor.[1 · Oct 23, 2026; 3 · Oct 29, 2026]
When the measurement fits two sizes (a 16 in inseam can suit a 12 or 14 in bike, for example), confidence matters: a smaller bike with an easy reach to the ground is easier to learn on.[1 · Oct 23, 2026; 3 · Oct 29, 2026]
How should a kids' bike fit?
- Seat height: on balance bikes and a first bike without training wheels, feet flat on the ground while seated; on training-wheel bikes and for confident pedalers, just the toes.[2 · Oct 29, 2026]
- Standover: standing over the bike with feet on the ground, an inch or two between your child and the top tube.[2 · Oct 29, 2026]
- Don't buy big to "grow into": a bike that is too big can slow learning and hurt confidence, and can compromise safety and stability.[2 3 · Oct 29, 2026]
- Try before you buy: sit your child on the bike to check they are comfortable and can reach the handlebars.[3 · Oct 29, 2026]
When to move to an adult bike
Trek suggests looking at adult bikes once a child is older than 12 and/or taller than about 4'8".[2 · Oct 29, 2026] Adult bikes are sized by frame, not wheel: see the road bike size chart and mountain bike size chart.
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Sources: 1. REI Expert Advice, How to choose a kids' bike. 2. Trek, Kids bike buyer's guide by age and size (re-checked Oct 29, 2026). 3. BikeRadar, Bike sizes for kids (re-checked Oct 29, 2026). Checked Oct 23, 2026.