Three Phase Power Calculator

Step-by-Step Guide

1. 1Select a Calculation Mode: Choose to calculate Power, Current, or Voltage, depending on which value you don't already know.
2. 2Enter Your Known Values: Enter line voltage, line current, or power, along with power factor, depending on the selected mode.
3. 3Enter Frequency for Reference: Input system frequency (50Hz or 60Hz) for documentation purposes.
4. 4Read the Calculated Result: View the requested value plus real power (kW), apparent power (kVA), and reactive power (kVAR).
5. 5Review the Step-by-Step Derivation: See exactly how √3, voltage, current, and power factor combine at each stage.

What This Calculator Provides

• ✓Real-time calculation as you type
• ✓Three modes: power, current, voltage
• ✓Real power (kW), apparent power (kVA), reactive power (kVAR)
• ✓50Hz and 60Hz system support
• ✓Full step-by-step derivation with √3 shown explicitly
• ✓Six built-in industrial voltage presets
• ✓Calculation history
• ✓Export as text or CSV file
• ✓No signup required

Pro Tips

• 💡Always confirm you're using line voltage (between two phases), not phase voltage (between phase and neutral), as the V input — this calculator's formulas expect line voltage throughout.
• 💡For motor cable and protection sizing, use Current mode with the motor's rated kW and rated power factor from the nameplate, then apply the standard 1.25× continuous load factor on top of the calculated current.
• 💡Use kVA (apparent power), not kW (real power), when sizing generators, transformers, or UPS systems — these components must handle the full current draw regardless of the load's power factor.
• 💡When comparing calculated power against a utility meter reading, remember the meter reads real power (kW) for energy billing purposes — apparent power (kVA) is what determines demand charges on many commercial tariffs.
• 💡Keep frequency-appropriate presets in mind when working across regions — 400-415V/50Hz systems are standard in Europe and much of Asia, while 480V/60Hz is standard for North American industrial systems.

Common Mistakes to Avoid

• ✕Forgetting the √3 factor and using the single-phase formula (V × I × PF) for a three-phase system. This underestimates power by roughly 42% — always confirm the √3 term is included for any three-phase calculation.
• ✕Using phase voltage instead of line voltage in the formula. In a star-connected system, line voltage is √3 times phase voltage — mixing these up produces a result off by that same factor.
• ✕Assuming a perfectly balanced three-phase load when the actual system is unbalanced. This calculator's formulas assume equal current in all three lines — an unbalanced load requires per-phase analysis instead.
• ✕Confusing kW and kVA when specifying generator or transformer capacity. Rating equipment in kW when kVA is needed undersizes it by a factor equal to 1 divided by the power factor.
• ✕Using nominal voltage (415V, 480V) when actual supply voltage differs. Real supply voltage can vary by several percent from nominal, which directly affects calculated current and power figures for precision applications.