The Bicycle Gear Inches calculator computes "gear inches" for your bike from the gear ratio and the tire diameter. This is useful because the distance a bike moves for every pedal rotation is equal to π*(gear inches). This is used for converting bike pedal rpm's to speed: if the "gear inches" is in inches, bike speed in mph is equal to (Gear inches)x(rpm)/336. Or you can use this handy bike rpm to speed calculator instead of using the formula.
INSTRUCTIONS: Choose units and enter the following:
Geer Inches (GI): The calculator will return the "Gear inches" in units of inches (or whatever length unit you prefer.)
This calculator computes "gear inches" (G) from the tire diameter (D) and the ratio of teeth in the front/chainring gear (Nf) to back/freewheel/cassette gear (Nb). Tire diameter default unit is inches, as is gear inches.