Road bike size calculator
A starting frame size and saddle height from your inseam. Your height alone is not enough.
Starting point only. Sizes differ between brands — compare the brand's stack and reach. (BikeRadar, Canyon)
How to measure your inseam
Barefoot, back against a wall, feet about 15 cm apart. Pull a book or a carpenter's square up firmly into the crotch and measure from its top edge to the floor. Do it two or three times and take the average (Colorado Cyclist).
Road bike size chart by inseam
The same formulas, every 2.5 cm.
| Inseam | Frame, centre to centre | Frame, centre to top | Saddle height |
|---|---|---|---|
| 70.0 cm | 45.5 cm | 46.9 cm | 61.8 cm |
| 72.5 cm | 47.1 cm | 48.6 cm | 64.0 cm |
| 75.0 cm | 48.8 cm | 50.2 cm | 66.2 cm |
| 77.5 cm | 50.4 cm | 51.9 cm | 68.4 cm |
| 80.0 cm | 52.0 cm | 53.6 cm | 70.6 cm |
| 82.5 cm | 53.6 cm | 55.3 cm | 72.8 cm |
| 85.0 cm | 55.2 cm | 57.0 cm | 75.1 cm |
| 87.5 cm | 56.9 cm | 58.6 cm | 77.3 cm |
| 90.0 cm | 58.5 cm | 60.3 cm | 79.5 cm |
| 92.5 cm | 60.1 cm | 62.0 cm | 81.7 cm |
| 95.0 cm | 61.8 cm | 63.7 cm | 83.9 cm |
How this is calculated
frame (centre to centre) = 0.65 × inseam (LeMond / Guimard) · frame (centre to top) = 0.67 × inseam · saddle height = 0.883 × inseam, from the centre of the bottom bracket to the top of the saddle · Hamley: 1.09 × inseam, measured to the pedal.
These are rules of thumb, not measurements of your body: a 2005 study of 19 trained cyclists found the LeMond and Hamley heights the same on average, and neither reliably gave the knee angle fitters aim for. Sources: Colorado Cyclist, How To Fit Your Custom Bicycle — https://www.coloradocyclist.com/bikefit; Peveler et al. 2005, JEPonline 8(1):51-55 — https://lida.sport-iat.de/twm/Record/4010655?lng=en; BikeRadar 24 Sep 2024 — https://www.bikeradar.com/advice/buyers-guides/road-bike-sizing ; Canyon 15 Aug 2025 — https://www.canyon.com/en-us/blog-content/advice/road-bike-size-guide/b30112022.html.
Runs in your browser: no cookies, nothing you enter is sent anywhere.
Other tools: Gear ratio calculator · Cycling calorie calculator · FTP and W/kg calculator · Road bike tyre pressure