Motor Efficiency Calculator
Quickly compute motor efficiency from input power, output power, voltage, current, and PF. Get losses and helpful formulas for single- or three-phase motors.
induction motor efficiency tool
Motor efficiency = output power/ input power x 100. Measuring and calculating the referring input power of voltage, current, and power factor, measuring output as shaft power (kW or hp). Losses = Input -- Output.
Formula & Table Summary:
- η(%) = (Pout/Pin) × 100
- 3φ: Pin = √3 × VL × IL × PF
- 1φ: Pin = V × I × PF
- Pout = (2π × N × τ)/60
- 1 hp = 0.746 kW; Ploss = Pin − Pout
Input: V, I, PF (+hp or τ & rpm) → Pin. Output: kW (or hp) → Pout. Returns η% and losses with validation if Pout > Pin.
three phase motor efficiency
Use this motor efficiency calculator to estimate the usefulness of a motor to convert electrical energy to mechanical energy. Input power can be obtained by entering voltage, current, and power factor in single or three-phase loads. Insert regulated output power (kW or hp), or torque and speed, and the tool gives the efficiency(% ) and losses (kW). It is a recommended method to size motors to determine equivalent solution and to detect excessively high losses in the field. The calculator does synoptic calculations (hp kW), will calculate the input of three-phase as V I 3P F, and it highlights inputs as greater than their outputs. Apply to induction motors, pumps, fans, and conveyors. Compare operating results against nominal nameplate data to determine whether a motor is operating close to its efficiency curve. The short and sweet form supply sheet and sample data table allow technicians to check readings and record audits. Set up to target low competition keywords, this page will create rankings on certain calculator-related queries and provide a reader with precise calculations made in an engineer-friendly manner.
motor performance table
| Case | Phase | V (V) | I (A) | PF | Pin (kW) | Pout (kW) | η (%) | Losses (kW) |
|---|---|---|---|---|---|---|---|---|
| 1 | 3φ | 400 | 32 | 0.86 | 19.1 | 16.5 | 86.4 | 2.6 |
| 2 | 1φ | 230 | 18 | 0.90 | 3.73 | 3.10 | 83.1 | 0.63 |
| 3 | 3φ | 415 | 48 | 0.82 | 28.3 | 24.0 | 84.8 | 4.3 |
Frequently Asked Questions - Motor Efficiency Calculator:
What is motor efficiency?
It is the ratio of shaft output power to electrical input power, expressed as a percentage.
How do I calculate three-phase input power?
Use Pin = √3 × VL × IL × PF (kW if VL in kV).
Can I use hp instead of kW?
Yes. Convert with 1 hp=0.746 kW or enter hp directly if supported.
What if output exceeds input?
Measurement error—check instruments, PF, wiring, and units.
Does speed affect efficiency?
Indirectly. Load and slip change with speed, affecting losses and efficiency.
Which PF should I use?
Use the real power factor at the motor terminals from a meter or VFD readout.
How do I get output power without a dynamometer?
Use torque sensor or infer from pump/fan curves and rpm; otherwise use nameplate rating cautiously.
Do voltage unbalance or harmonics matter?
Yes, they increase losses and reduce efficiency; fix supply quality issues first.
Is nameplate efficiency the same as field efficiency?
Not always—field efficiency varies with load, temperature, and supply conditions.
What is a good efficiency?
Premium motors often exceed 90% at rated load; smaller or lightly loaded motors are lower.
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