Sprocket ratio calculator

Enter the tooth counts and driving speed to calculate reduction ratio and theoretical driven sprocket RPM.

Drive ratioEnter values to calculate

The larger driven sprocket turns more slowly

A 15-tooth driving sprocket and 45-tooth driven sprocket produce a 3:1 reduction. At 3,000 driving RPM, the driven sprocket turns at 1,000 RPM.

The result excludes the rest of the system

Tire diameter, other transmission stages, chain pitch, center distance, load, losses and component speed ratings are outside this calculation.

More tools

Tire dimensions

Calculate theoretical diameter and circumference.

Tire comparison

Compare the geometry of two metric tire labels.

Speedometer error

Estimate geometric speed change from tire diameter.

RPM & road speed

Relate speed and RPM through tire and gear ratios.

Two-stroke mix

Calculate oil from a manufacturer-specified ratio.

Wheel offset

Compare inner clearance and outer wheel position.

Compression ratio

Calculate static ratio from cylinder and clearance geometry.

Engine displacement

Calculate total displacement from bore, stroke and cylinders.

Power to weight

Compare horsepower and vehicle weight in common units.

Injector size

Estimate per-cylinder fuel flow from explicit assumptions.