Direct current
P = U * I * η
Alternating single-phase
P = U₀ * I * cosφ * η
Alternating two-phase
P = U * I * cosφ * η
Alternating three-phase
P = √3 * U * I * cosφ * η
η = Efficiency(%)
P = Power (W)
U₀ = Voltage [L - N] (V)
U = Voltage L - L(V)
I = Current(A)
cosφ = Power factor
Estimate motor output power in kW or HP from amps, voltage, PF, and efficiency—no nameplate needed. Works for single & three-phase motors.
Identify unknown motor size when the nameplate is missing, damaged, or painted over
Verify if a motor matches its documented specifications during commissioning
Estimate actual mechanical load during energy audits or preventive maintenance
The calculator first determines electrical input power, then applies motor efficiency to estimate mechanical output power:
Direct current: Pout = Pout = V × I × η
Single-phase: Pout = V × I × PF × η
Two-phase: Pout = V × I × PF × η
Three-phase: Pout = √3 × V × I × PF × η
Results are displayed in both kW and horsepower (HP), where 1 HP ≈ 0.746 kW.
Direct current: Pout = √3 × 400 × 10 × 0.85 × 0.90 ≈ 5,450 W = **5.45 kW** HP = 5.45 ÷ 0.746 ≈ **7.3 HP**
Three-phase motor: 400 V, 10 A, PF = 0.85, η = 90% → Output ≈ 5.45 kW (7.3 HP)
Two-phase: Pout = 230 × 5 × 0.80 × 0.80 = 736 W = **0.74 kW** HP = 0.74 ÷ 0.746 ≈ **1.0 HP**
Single-phase motor: 230 V, 5 A, PF = 0.80, η = 80% → Output ≈ 0.74 kW (1.0 HP)
Use typical estimates if exact values are unknown: PF ≈ 0.8–0.9, Efficiency ≈ 85–95% (for motors under load)
Measure current at full or known load—idle or light-load readings will underestimate true power
This tool estimates mechanical output power, not electrical input from the grid
Industrial maintenance teams identifying legacy motors
Energy auditors assessing motor system efficiency
Facility engineers verifying replacement motor compatibility
Contractors troubleshooting HVAC or pump systems on-site
Technical educators demonstrating real-world motor performance
1.Maintenance Technicians – Quickly assess motor health and sizing in the field
2.Plant Engineers – Validate motor performance during system upgrades
3.Energy Consultants – Support energy-saving recommendations with real data
4.Electricians – Confirm motor specs before rewiring or protection setup
5.Facility Managers – Plan capital budgets for motor replacements
This calculator implements standard IEEE and IEC methodologies for estimating motor output power from operational parameters. For best accuracy:
1.Use a calibrated clamp meter to measure current
2.Measure line-to-line voltage under load
3.If PF is unknown, assume 0.85 for three-phase induction motors
4.If efficiency is unknown, use 90% for motors >5 HP under full load
5.Avoid using this tool for variable frequency drive (VFD)-fed motors unless harmonics are accounted for
You need four values: voltage, current (amps), power factor, and efficiency. For a three-phase motor, mechanical power (HP) = (√3 × V × I × PF × η) / 746. Our tool does this instantly.
Yes. As long as you can measure voltage and current under load—and estimate reasonable PF and efficiency—you can reliably estimate the motor’s output power in kW or HP.
Input power is what the motor draws electrically (kW). Output power is what it delivers mechanically at the shaft (kW or HP). Due to losses (heat, friction), output is always less than input. This tool estimates output power.
Without power factor, you’d assume all current contributes to useful work—which isn’t true in AC systems. Without efficiency, you’d ignore internal losses. Both are essential for accurate mechanical power estimation.
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