Bike size finder
Frame size from your height and inside leg, plus the saddle height to start from. Works for road, hybrid, mountain and children's bikes.
How to measure yourself
Two numbers, both taken at home with a tape measure and a wall.
- Height: against a wall, barefoot, heels together, looking straight ahead.
- Inside leg: stand against the wall and hold a book firmly between your legs at crotch height, as if it were a saddle. Measure from the floor to the top of the book. This is not your trouser inside leg — it is usually 2-4 cm longer.
Height alone gets you to the right size band. Inside leg decides the saddle height and, if you are near a boundary, which of two frame sizes to choose.
The frame size table for adults
These are the conventional bands, and they are accurate enough to narrow the choice to one or two sizes:
| Rider height | Frame (cm) | Frame (inches) | Letter |
|---|---|---|---|
| 150-157 cm (4'11"-5'2") | 47-50 | 14-15.5" | XS |
| 157-165 cm (5'2"-5'5") | 50-53 | 15.5-16.5" | S |
| 165-173 cm (5'5"-5'8") | 53-55 | 16.5-17.5" | M |
| 173-180 cm (5'8"-5'11") | 55-57 | 17.5-18.5" | M/L |
| 180-185 cm (5'11"-6'1") | 57-59 | 18.5-19.5" | L |
| 185-193 cm (6'1"-6'4") | 59-62 | 19.5-21" | XL |
Mountain bike frames are quoted in inches, road frames in centimetres. That is a convention, not a conversion: 18 inches on a mountain bike is not the same frame as 18 inches on a road bike.
Saddle height, which matters more than frame size
Once the frame is right, saddle height decides whether the bike is comfortable. A starting figure is inside leg × 0.883, measured from the centre of the bottom bracket to the top of the saddle along the seat tube. The calculator gives you that number.
Then check it with the heel method: with your heel on the pedal at the bottom of the stroke, the leg should be almost straight with a slight bend. If your hips rock when you pedal, it is too high.
Children: age is a poor guide
Two seven-year-olds can differ by 15 cm. Use inside leg, and check it against the bike's minimum saddle height — that is what decides whether the child can put both feet down.
| Inside leg | Wheel size |
|---|---|
| 35-42 cm | 12 inch |
| 40-48 cm | 14 inch |
| 45-53 cm | 16 inch |
| 52-60 cm | 20 inch |
| 58-68 cm | 24 inch |
| 66 cm and up | 26 inch or a small adult bike |
If a child is between two sizes, take the smaller one. A bike that is too big is unsafe and unpleasant, and children grow out of them faster than they wear them out.