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Motor Efficiency Calculator

Calculate electric motor efficiency from mechanical output and electrical input power.

Introduction

Motor Efficiency Calculator — Calculate electric motor efficiency from mechanical output and electrical input power. Enter Mechanical output power (W), Voltage (V), Current (A), Power factor, Phase to get an instant, accurate result.

Formula

Efficiency (%) = (Mechanical Output Power ÷ Electrical Input Power) × 100, where Input Power = V × I × PF (single-phase) or √3 × V × I × PF (three-phase).

Step-by-step

  1. Enter the Mechanical output power (W).
  2. Enter the Voltage (V).
  3. Enter the Current (A).
  4. Enter the Power factor.
  5. Enter the Phase.
  6. Click Calculate to see your result instantly.

Real-world example

Example: With Mechanical output power (W) = 3000, Voltage (V) = 230, Current (A) = 20, Power factor = 0.85, Phase = no, the Motor Efficiency Calculator gives Input Power W: 3910, Efficiency Pct: 76.7263.

Frequently Asked Questions

Why is efficiency always less than 100%?
Real motors lose some input electrical energy to heat from winding resistance, friction, and magnetic losses in the core, so the mechanical output power is always somewhat less than the electrical input power.
Where do I find a motor's output power?
It's usually on the nameplate in horsepower or kW — convert horsepower to watts (× 745.7) first if needed so the units match the electrical input power.
What inputs does the Motor Efficiency Calculator need?
You'll need to provide: Mechanical output power (W), Voltage (V), Current (A), Power factor, Phase. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Motor Efficiency Calculator?
The Motor Efficiency Calculator applies the formula exactly as calculated — Efficiency (%) = (Mechanical Output Power ÷ Electrical Input Power) × 100, where Input Power = V × I × PF (single-phase) or √3 × V × I × PF (three-phase). — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Motor Efficiency Calculator free to use?
Yes, the Motor Efficiency Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Motor Efficiency Calculator

The Motor Efficiency Calculator uses a real, verifiable formula — Efficiency (%) = (Mechanical Output Power ÷ Electrical Input Power) × 100, where Input Power = V × I × PF (single-phase) or √3 × V × I × PF (three-phase). — so results are accurate every time, not an approximation.