Electrical Reference Card
One page. Voltage drop lengths, breaker and wire pairing, motor FLC.
$3.99
BuyThree-Phase Power Calculator — kVA, kW, Current & Power Factor
Enter line voltage, line current, and power factor to calculate apparent power, real power, reactive power, and the power triangle for any three-phase system.
Calculate kVA, kW, kVAR, phase voltage, and phase current for Wye or Delta systems. See the Three-Phase Power Guide for formulas, voltage levels, and field troubleshooting.
Three-phase power formulas
| Quantity | Formula | Units |
|---|---|---|
| Apparent power | S = √3 × VL × IL | kVA (÷1000) |
| Real power | P = S × PF | kW |
| Reactive power | Q = √(S² − P²) | kVAR |
| Wye phase voltage | Vphase = VL / √3 | Volts |
| Delta phase voltage | Vphase = VL | Volts |
| Wye phase current | Iphase = IL | Amps |
| Delta phase current | Iphase = IL / √3 | Amps |
VL = line voltage (L-L) · IL = line current · PF = power factor (0–1)
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Quote electrical work and flag panel headroom before you price it.
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Card, 15-page guide and the estimator workbook. All six files.
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Three-phase electrical tools
Clamp meters, multimeters, and voltage testers for measuring line current and verifying voltage before connecting loads.
Klein Tools CL800 Digital Clamp Meter 1000V
- Measuring line current on three-phase panels
- Motor circuit troubleshooting
- True-RMS AC/DC up to 600A
- 1000V CAT IV safety rating
Fluke 117 Digital Multimeter Non-Contact AC Voltage
- Verifying line and phase voltage
- Before connecting loads
- True-RMS with non-contact detection
- Industry standard for electricians
Ideal 61-757 600A AC/DC TRMS TightSight Clamp Meter
- High-current measurement
- Industrial three-phase circuits
- 600A AC/DC true-RMS
- TightSight flexible display
Klein Tools NCVT-6 Non-Contact Volt Tester with Laser Distance
- Quick voltage presence checks
- Before panel work
- Non-contact detection
- Built-in laser distance meter
Square D QO120 Miniature Circuit Breaker 20A
- Reference breaker for panel work
- Circuit sizing reference
- Industry-standard 20A single-pole
- QO series plug-on design
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Apparent Power vs. Real Power
Apparent power (kVA) is what your conductors, breakers, and transformer must be sized to handle — it's the total current-carrying demand regardless of power factor. Real power (kW) is the portion of that doing actual useful work: turning motors, producing heat, generating light. The gap between them is reactive power (kVAR), which oscillates between the source and any inductive or capacitive loads without doing net work. A panel showing 100 kVA at 0.80 power factor is only delivering 80 kW of real output, but every wire upstream still has to carry the full 100 kVA worth of current.
Wye vs. Delta — Why the Toggle Matters
Selecting the correct system type changes how this calculator relates line and phase values. In a Wye system, phase voltage is line voltage divided by √3, and phase current equals line current directly. In a Delta system, phase voltage equals line voltage directly, and phase current is line current divided by √3. Confusing these relationships is the single most common error in three-phase fieldwork — always confirm your system type by measuring phase-to-neutral voltage before assuming a Wye configuration with an available neutral.
Reading Your Power Factor Result
Power factor below 0.85 commonly triggers demand charges or surcharges on commercial and industrial utility bills, since the utility must size its own infrastructure for the higher kVA demand even though only the kW portion is "useful" energy. Power factor correction capacitors installed near large motor loads cancel lagging reactive current and can bring a facility from 0.75–0.80 up to 0.95 or better, reducing both utility penalties and the heating losses in upstream conductors. If this calculator shows a PF angle above 25–30°, it's worth evaluating correction options.
Sizing Conductors and Breakers from These Results
Once you have line current from this calculator, conductor and breaker sizing follows NEC rules: continuous loads require conductors and breakers rated at 125% of the calculated current per NEC 210.19 and 210.20(A). For motor circuits, use the motor's nameplate FLA rather than a calculated current, and apply NEC 430.22 (125% for conductors) and NEC 430.52 (up to 250% for inverse-time breaker OCPD) instead of the general continuous-load rules. This calculator gives you the real-world current draw; the NEC articles tell you how to size protection around it.
Related Calculators & Guides
- Three-Phase Power Guide — Voltage, Current, kVA & Power Factor
- Motor Full-Load Amps (FLA) Calculator
- Commercial Load Calculator — NEC Article 220
- Series & Parallel Circuit Calculator
- Series & Parallel Circuits Guide
- Ohm's Law & Power Calculator
- Panel Schedule Calculator
- Circuit Breaker Sizing Calculator
- Transformer Sizing Calculator — kVA, Primary & Secondary Current
- Transformer Sizing Guide — kVA, Voltage & Selection
- Motor Circuit Sizing Calculator — NEC 430 Conductors, Breaker, Overload & Disconnect
- Motor Circuit Sizing Guide — Conductors, Breakers, Overloads & Disconnects per NEC 430
- Feeder / Service Load Calculator
- → Three-Phase Power Chart