About this Gear Ratio Calculator

Quickly estimate overall gear reduction, output speed (RPM), and output torque for single- or multi-stage gear trains. Enter tooth counts or a known ratio for each stage, set efficiency, and see results instantly.

Why it’s useful

  • Compare gear sets and stage counts in seconds.

  • Works with teeth or a direct ratio (Driven ÷ Driver).

  • Includes per-stage efficiency to better approximate real-world output.

Industrial Gearbox Supply Logo

Gear Ratio Calculator

Compute per-stage & overall ratio, output speed, and torque.
Tip: You can override efficiency per stage in the table.
1 stage
# Driver Teeth Driven Teeth or Direct Ratio (Driven ÷ Driver) Stage Eff. (%) Stage Ratio
S1 —
How it works: Stage Ratio = Driven ÷ Driver. Overall Ratio = product of all stage ratios (reduction > 1.00). Output Speed = Input Speed ÷ Overall Ratio. Output Torque ≈ Input Torque × Overall Ratio × (product of efficiencies).
Overall Ratio
—
Cumulative Efficiency
—
Output Speed (RPM)
—
Output Torque (N·m)
—
Stage Driver Driven Direct Ratio Used Ratio Eff. Used
Note: Results are idealized; real systems vary with load, lubrication, and alignment.
Questions? Call us at (517) 858-2966 or visit industrialgearboxsupply.com

How to use

  1. Enter your Input Speed (RPM).

  2. (Optional) Enter your Input Torque (N·m).

  3. Set a Default Stage Efficiency (%)—you can override it per stage.

  4. For each stage, either:

    • Enter Driver Teeth and Driven Teeth, or

    • Enter a Direct Ratio (Driven ÷ Driver).

  5. Add or remove stages as needed. Results update automatically.

  6. Review Overall Ratio, Cumulative Efficiency, Output Speed (RPM), and Output Torque (N·m) in the results panel.

Tips

  • Stage Ratio = Driven ÷ Driver. For reductions, ratios are greater than 1.00.

  • Output Speed = Input Speed ÷ Overall Ratio.

  • Output Torque ≈ Input Torque × Overall Ratio × (product of efficiencies).

  • If you don’t enter Input Torque, torque won’t be calculated (speed and ratios still will).

  • Real systems vary with load, lubrication, temperature, and alignment; treat results as estimates.

Need help selecting a gearbox or verifying a design? Call (517) 858-2966 or visit industrialgearboxsupply.com.

You can also review our other calculators and tools: