When to Use This Calculator
Use this calculator for balanced three-phase loads when line-to-line voltage, line current, and power factor are known or measured. It is best for steady-state kW and kVA estimates, not fault, starting, or protection studies.
Enter Values
Formula Summary
For balanced three-phase power:
kW = √3 × V × A × PF ÷ 1000
kVA = √3 × V × A ÷ 1000
Where:
- V = line-to-line voltage
- A = current in amps
- PF = power factor
- √3 ≈ 1.732
Practical Examples
480 V motor load
480 V, 100 A, PF = 0.90
kW = 1.732 × 480 × 100 × 0.90 ÷ 1000
kW = 74.82 kW
kVA = 1.732 × 480 × 100 ÷ 1000
kVA = 83.14 kVA
600 V process load
600 V, 55 A, PF = 0.92
kW = 1.732 × 600 × 55 × 0.92 ÷ 1000
kW = 52.59 kW
Using the Correct Values
- Voltage: enter RMS line-to-line voltage, not line-to-neutral voltage.
- Current: enter RMS line current for the balanced load.
- Power factor: use the load's actual power factor when available.
The square-root-of-three multiplier is appropriate when line-to-line voltage and line current are used for a balanced three-phase system.
Assumptions and Limitations
This calculation assumes a balanced sinusoidal load. It does not separately model phase imbalance, harmonics, neutral current, voltage distortion, demand, motor efficiency, or transient starting current.
Do not use calculated running kW or kVA alone to size motor circuits, generators, transformers, conductors, or overcurrent protection.
Common Mistakes
- Entering line-to-neutral voltage instead of line-to-line voltage.
- Using a nameplate maximum current when you need measured operating load, or the reverse.
- Forgetting that low power factor reduces kW for the same kVA and current.
- Applying the balanced formula to a heavily unbalanced or harmonic-rich load.
Reference Notes
The square-root-of-three relationship is the standard balanced three-phase power formula used in power and circuit analysis. Equipment sizing should be checked against nameplates, manufacturer data, and the applicable electrical code rather than this simplified result alone.