About

Optimizing bicycle performance requires understanding the mechanical relationship between pedal input and forward velocity. Cyclists and mechanics use this data to select appropriate chainrings and cassettes for specific terrains. By analyzing the gear inches and tire circumference, one can determine the precise speed at a given pedaling rhythm (cadence).

This tool eliminates the guesswork in gear selection. It allows users to input their drivetrain specifics and wheel parameters to output the theoretical speed, disregarding wind resistance and friction losses.

Formulas

The speed v is a function of cadence C (RPM), the gear ratio (N_front / N_rear), and wheel circumference W_circ.

v = C × N_frontN_rear × W_circ × k

Where k is the unit conversion constant (e.g., converting mm/min to km/h).

Reference Data

Tire Size (ISO)	Circumference (mm)	Common Use
23-622 (700x23c)	2096	Road Racing
25-622 (700x25c)	2105	Road Endurance
28-622 (700x28c)	2136	Commuting/Road
32-622 (700x32c)	2155	Gravel/Touring
40-622 (700x40c)	2200	Gravel
50-559 (26x1.95)	2050	MTB 26"
54-584 (27.5x2.1)	2148	MTB 27.5"
57-622 (29x2.25)	2288	MTB 29"

Frequently Asked Questions

Cadence is the rate at which a cyclist pedals, measured in Revolutions Per Minute (RPM). Professional cyclists typically maintain 90-100 RPM.

Yes, slightly. Lower pressure reduces the effective radius of the wheel under load, decreasing the circumference. This calculator assumes standard inflation.

This calculator outputs theoretical speed. Real-world speed is reduced by air resistance (drag), rolling resistance, and drivetrain friction.

Gear inches is a unit that describes the distance the bike travels with one revolution of the pedals, relative to a theoretical wheel diameter.