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Calcimator

Gear Ratio Calculator

Calculate gear ratio, output speed, output torque, and mechanical advantage for a simple gear pair.

Inputs

RPM
ft·lb

Results

Gear Ratio

3:1

Output Speed

600 RPM

Output Torque

147 ft·lb

Speed Reduction66.7%
Mechanical Advantage2.94
How to Use This Calculator
  1. Enter the number of teeth on the Driver Gear (pinion) — the input gear connected to the motor.
  2. Enter the number of teeth on the Driven Gear — a larger tooth count reduces output speed and multiplies torque.
  3. Enter the Input Speed in RPM — common motor speeds are 1200, 1800, and 3600 RPM.
  4. Enter the Input Torque in ft·lb, or calculate it as T = 5252 × HP / RPM.
  5. Read the Gear Ratio, Output Speed in RPM, and Output Torque in ft·lb — these are the key design values.
  6. Check the Mechanical Advantage and Speed Reduction % to confirm they meet your application requirements.

How the result changes with Driver Gear Teeth

Driver Gear TeethGear RatioOutput SpeedOutput Torque
571.05:11,710 RPM51.58 ft·lb
1800.33:15,400 RPM16.33 ft·lb
3280.18:19,840 RPM8.96 ft·lb
4510.13:113,530 RPM6.52 ft·lb

What each input means

Driver Gear Teeth
Number of teeth on the driving (input) gear or pinion. Minimum practical tooth count is ~12 for spur gears.
Driven Gear Teeth
Number of teeth on the driven (output) gear. Larger tooth count means more speed reduction and torque multiplication.
Input Speed
Rotational speed of the driver gear, typically from a motor. Common motor speeds: 1200, 1800, 3600 RPM.
Input Torque
Torque available from the driving source. T = 5252 × HP / RPM.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Driver Gear Teeth = 20, Driven Gear Teeth = 60, Input Speed = 1800, Input Torque = 50 = 4 input(s) provided
  2. Calculate Gear Ratio
    Gear Ratio
    3 = 3
  3. Calculate Output Speed
    Output Speed
    600 = 600
  4. Calculate Output Torque
    Output Torque
    147 = 147
  5. Calculate Speed Reduction
    Speed Reduction
    66.7 = 66.7
  6. Calculate Mechanical Advantage
    Mechanical Advantage
    2.94 = 2.94

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