Bike Gear Ratio Calculator

Enter Calculation

Chainring Teeth:

Cog Teeth:

Wheel Diameter (inches):

Results

Input	Value
Chainring Teeth	50
Cog Teeth	15
Wheel Diameter	27 inches

Result	Value
Gear Ratio	3.33
Gear Inches	90
Development	23.56 feet
Speed at 90 RPM	2 mph

Understanding the Results:

• Gear Ratio: The number of turns the rear wheel makes for each pedal revolution. Higher ratio means harder pedaling but more speed.
• Gear Inches: A traditional measure of gear size. It represents the diameter of an equivalent direct-drive wheel.
• Development: The distance traveled in one complete revolution of the pedals.
• Speed at 90 RPM: The theoretical speed when pedaling at 90 revolutions per minute.

With the current setup (50 teeth chainring and 15 teeth cog), for every complete pedal rotation, the rear wheel turns 3.33 times.