How to use the electric motor efficiency calculator
Find the efficiency of an electric motor from its electrical input and mechanical output. Enter supply voltage, supply current, shaft speed, shaft torque in the fields above; the electrical input power, mechanical output power, motor efficiency are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “motor efficiency”, “how efficient is my motor”, “electrical to shaft power”, “calculate electric motor efficiency”, “find electrical input power”.
Formula
Variables
- V — Supply voltage (V)
- I — Supply current (A)
- rpm — Shaft speed (rpm)
- T — Shaft torque (N·m)
Worked example
With supply voltage = 24 V, supply current = 5 A, shaft speed = 2000 rpm, shaft torque = 0.1 N·m, the calculator gives electrical input power ≈ 120 W; mechanical output power ≈ 20.94395 W; motor efficiency ≈ 17.45329 %.
Frequently asked questions
What is the electric motor efficiency calculator used for?
Find the efficiency of an electric motor from its electrical input and mechanical output. It helps with questions such as “motor efficiency”, “how efficient is my motor”, “electrical to shaft power”.
What is the formula for the electric motor efficiency calculation?
Electrical input power (W) = V × I. Mechanical output power (W) = T × 2 × π × rpm / 60. Motor efficiency (%) = [Mechanical output power] / [Electrical input power] × 100. Here V is supply voltage (V), I is supply current (A), rpm is shaft speed (rpm), T is shaft torque (N·m).
What inputs do I need for the electric motor efficiency calculator?
You need supply voltage in V, supply current in A, shaft speed in rpm, shaft torque in N·m. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the electric motor efficiency calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the electric motor efficiency result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.