Gear Ratio & RPM Calculator

Quickly estimate speed at RPM (or RPM at speed) using tire diameter, transmission ratio, and diff ratio. Great for swap planning and gearing decisions.

Client-side only No tracking Print-friendly

Tip

Use 1.00 for 4th gear (1:1).

Most common benchmark.

Inputs

Set your drivetrain

All values are in inches, ratios, mph, rpm.

Tire diameter (in)

Diff ratio

Transmission ratio (selected gear)

RPM

MPH

HP Estimator Parts Builder

Outputs

Quick results

Uses the standard 336 constant formula.

Speed at RPM: —

RPM at speed: —

Speed table

RPM steps up to your selected RPM

RPM	MPH