TORQDEX // DRIVE-01

RPM & Gear Ratio Calculator

Estimate engine RPM from road speed, tire diameter, axle ratio, and transmission gear ratio.

INPUT DATA

MPH
in
:1
:1

RESULT

ESTIMATED ENGINE RPM -- RPM
OVERALL DRIVE RATIO -- :1
TIRE REVOLUTIONS / MILE --
CALCULATION STATUS WAITING FOR DATA

Enter speed, tire diameter, axle ratio, and gear ratio.

01 // HOW IT WORKS

What affects cruising RPM?

Tire diameter

Taller tires travel farther per revolution and generally reduce engine RPM at a given road speed.

Axle ratio

A numerically higher axle ratio increases engine RPM at a given speed and generally multiplies torque more.

Transmission ratio

A 1.00 gear ratio is direct drive. Overdrive gears use a ratio below 1.00 and reduce engine RPM at cruising speed.

FORMULA

Engine RPM

RPM = (MPH × Axle Ratio × Gear Ratio × 336) ÷ Tire Diameter

This is a common approximation for a non-slipping drivetrain. Automatic transmission torque-converter slip can make actual RPM slightly different when the converter is unlocked.