Gear Ratio Calculator | Speed & Torque

Formula

This calculator uses the standard gear ratio calculator formula:

Gear Ratio Formula

GR = T_driven / T_driver = N_input / N_output

Frequently Asked Questions

What is a gear ratio? ⌄

A gear ratio is the ratio of the number of teeth on the driven gear to the number of teeth on the driver gear. GR = T_driven / T_driver.

How do I calculate output speed from gear ratio? ⌄

Output RPM = Input RPM ÷ Gear Ratio. For example, if the gear ratio is 3:1 and input speed is 1,500 RPM, output speed = 500 RPM.

How does gear ratio affect torque? ⌄

Output torque = Input torque × Gear Ratio. A higher gear ratio increases torque but reduces speed proportionally, assuming 100% efficiency.

What is a reduction gear ratio? ⌄

A reduction gear ratio is greater than 1:1, meaning the output shaft rotates slower than the input but with more torque. Typical in gearboxes for motors.

What gear ratio is used in cars? ⌄

Automotive transmissions use multiple gear ratios. Low gears (e.g. 3.5:1) give high torque for acceleration; high gears (e.g. 0.75:1) allow high-speed cruising with reduced fuel consumption.

How do I calculate compound gear ratios? ⌄

For a gear train with multiple stages, multiply individual ratios: Total GR = GR1 × GR2 × GR3. For example, 2:1 × 3:1 = 6:1 overall reduction.

⚙️ Gear Ratio Calculator