Electrical calculators
3-Phase Load Calculator
Calculate three-phase real power, apparent power, line current, phase current, and current imbalance for balanced or phase-by-phase Wye and Delta loads.
Three-phase load path
kW / A
kW / A
kW / A
Use line-to-line voltage. Balanced mode starts from total power; phase-by-phase mode checks how the current is distributed across A, B, and C.
Input Dimensions
Calculation Results
Planning estimate only
Results are based on the values and assumptions entered here. Confirm quantities with current product information and suppliers; use qualified local professionals for structural, safety-critical, permitted, or code-regulated work.
Read the calculator terms and limits →How to Use the 3-Phase Load Calculator
Choose Balanced total load when you know the total kW or kVA and want the estimated three-phase line current. Choose Phase-by-phase load when the real power is distributed across phases A, B, and C and you want to compare current between them. Enter the line-to-line voltage, select Wye or Delta, and enter the power factor.
The balanced calculation uses the standard relationship between three-phase power and line current. When kW is entered, the calculator converts it to kVA using power factor. When kVA is entered, it converts to kW and calculates current directly from apparent power.
Balanced Three-Phase Power
For a balanced three-phase load, the calculator uses I = kW × 1000 ÷ (√3 × VL-L × PF). If the known value is kVA, it uses I = kVA × 1000 ÷ (√3 × VL-L). The √3 factor is the line-to-line relationship used for total three-phase power. Schneider Electric’s transformer guidance also identifies 1.732 as the square-root-of-three factor for three-phase kVA calculations.
Power factor is the ratio of real power in kW to apparent power in kVA. A lower power factor means more current is required for the same useful real power, which can affect conductor and equipment sizing. These formulas assume RMS values and a sinusoidal, steady-state planning condition.
Wye, Delta, and Phase Imbalance
In the phase-by-phase mode, the calculator uses line-to-line voltage to derive the phase voltage for a Wye load. For a Delta load, phase voltage equals line-to-line voltage, while line current is √3 times the phase current for an ideal balanced Delta relationship. The result reports each phase current, the average, the maximum, and the percentage difference between the highest and lowest current.
Keeping phases reasonably balanced can reduce uneven conductor loading and unwanted neutral current in a four-wire Wye system. The neutral result here is an approximation based on current magnitudes and a common power-factor angle. Harmonics, nonlinear loads, different power factors, and actual phasor measurements can change the neutral current substantially.
Safety and Limitations
This calculator is a preliminary planning aid. It does not select a final breaker, conductor, transformer, disconnect, generator, or service size. Final design must consider applicable electrical code, continuous-load rules, motor starting current, fault current, conductor ampacity, temperature correction, raceway fill, installation method, protection, harmonics, equipment nameplates, phase sequence, grounding, and local utility requirements.
Have a qualified electrical professional review the complete load schedule before construction, energization, or equipment procurement. Do not work on energized equipment.
Frequently Asked Questions
What is the three-phase current formula?
For a balanced three-phase load, line current is I = kW × 1000 ÷ (√3 × line voltage × power factor), or I = kVA × 1000 ÷ (√3 × line voltage).
What is the difference between Wye and Delta?
In a Wye system, line voltage is √3 times phase voltage and line current equals phase current. In a balanced Delta system, line voltage equals phase voltage and line current is √3 times phase current.
How does the phase-by-phase mode work?
Enter the real power assigned to phases A, B, and C. The calculator estimates each phase current from the selected voltage, connection, and common power factor, then reports maximum current and imbalance.
Can this calculator size a three-phase breaker or cable?
No. It is a planning calculator only. Final sizing must account for code demand rules, continuous loads, motor starting current, conductor ampacity, temperature, installation method, protection, harmonics, and equipment ratings.
Technical reference: Schneider Electric three-phase kVA formula; University of Louisville ECE three-phase power lesson; Fluke balanced three-phase power overview.