A child should be able to touch the ground with the balls of both feet while seated. Buying too big to grow into makes a bike harder to control.
How the bike size calculator works
BikeSizeCalc sizes a frame from your inseam, the inside-leg length from the floor to your crotch. Road and gravel frames are inseam × 0.70 in centimetres, hybrid and city frames inseam × 0.685, and mountain bike frames inseam (cm) × 0.226 in inches. If you leave the inseam blank it is estimated as 46% of your height. The letter size (XS to XXL) comes from your height, because most brands now sell by letter and list a height range for each. Saddle height is inseam × 0.883, measured from the centre of the crank axle to the top of the saddle along the seat tube.
Bike size chart by height (estimated inseam)
| Height | Road frame | Road size | Mountain frame | Mountain size | Hybrid frame |
|---|---|---|---|---|---|
| 5′0″ (152 cm) | 49 cm | XS | 16 in | XS | 48 cm |
| 5′2″ (157 cm) | 51 cm | XS | 16.5 in | S | 50 cm |
| 5′4″ (163 cm) | 52 cm | S | 17 in | S | 51 cm |
| 5′6″ (168 cm) | 54 cm | S | 17.5 in | M | 53 cm |
| 5′8″ (173 cm) | 56 cm | M | 18 in | M | 54 cm |
| 5′10″ (178 cm) | 57 cm | L | 18.5 in | M | 56 cm |
| 6′0″ (183 cm) | 59 cm | L | 19 in | L | 58 cm |
| 6′2″ (188 cm) | 61 cm | XL | 19.5 in | L | 59 cm |
| 6′4″ (193 cm) | 62 cm | XXL | 20 in | XL | 61 cm |
Kids bike size by height
| Wheel size | Child height | Typical age |
|---|---|---|
| 12 in | under 98 cm | 2–4 |
| 14 in | 98–107 cm | 3–5 |
| 16 in | 108–119 cm | 4–6 |
| 20 in | 120–134 cm | 6–8 |
| 24 in | 135–149 cm | 8–11 |
| 26 in or adult XS | 150 cm and up | 10+ |
Frame sizes are a starting point. Geometry (stack, reach, top tube length) differs between brands and models, so compare with the maker’s size chart and test ride when you can. Fine-tune fit with saddle height, stem length and handlebar position.
Frequently asked questions
What size bike for a 6 year old?
Most 6 year olds are about 110–120 cm tall and ride a 16 in bike, moving to 20 in around age 7.
What size bike for a 10 year old?
Usually a 24 in wheel bike for a child about 135–149 cm tall.
When can a child ride an adult bike?
Around 150 cm (4′11″) tall, on a 26 in or adult XS frame.
Is BikeSizeCalc free?
Yes, with no sign-up or ads, and your numbers stay in your browser.
Are the results exact?
No. They are a starting point. Frame geometry varies by brand, so check the maker’s size chart and test ride.