Three-Phase Power Calculator
Enter the line voltage, line current and power factor to find the apparent power in volt-amps, the real power in watts and kilowatts, and the reactive power in volt-amps reactive. The calculation uses the standard balanced three-phase relations.
How to use the three-phase power calculator
- Enter the line-to-line voltage in volts.
- Enter the line current in amps.
- Enter the power factor between 0 and 1 (use 1 for a purely resistive load).
- Read the apparent, real and reactive power.
Examples
480 V, 100 A, power factor 0.8
lineVoltage = 480, lineCurrent = 100, powerFactor = 0.8
apparent = 83138.44 VA, real = 66510.75 W, reactive = 49883.06 VAR
Unity power factor
lineVoltage = 480, lineCurrent = 100, powerFactor = 1
real = apparent = 83138.44 W, reactive = 0 VAR
Frequently asked questions
What is the three-phase apparent power formula?
Apparent power equals the square root of 3 times the line voltage times the line current, S = sqrt(3) * V * I. With 480 V and 100 A the apparent power is about 83138 VA.
How do I get real power from apparent power?
Multiply the apparent power by the power factor, P = S * power factor. At a power factor of 0.8 a load drawing 83138 VA produces about 66511 W of real power.
How is reactive power calculated?
Reactive power equals the apparent power times sqrt(1 - power factor squared), Q = S * sqrt(1 - pf^2). It is zero when the power factor is 1 because the load is purely resistive.
Does this use line voltage or phase voltage?
It uses the line-to-line voltage with the sqrt(3) factor, which is the standard way three-phase ratings are stated. For a balanced load this matches 3 times the per-phase power.
What power factor should I enter?
Use 1 for a purely resistive load such as heaters, around 0.8 for typical motor loads, and the nameplate value for a specific machine. The value must be between 0 and 1.
Related tools
Power Factor Calculator
Calculate power factor, phase angle and reactive power from real and apparent power. Find pf, angle in degrees and VAR. Free electrical engineering tool.
Ohm's Law Calculator
Solve Ohm's law online. Enter any two of voltage, current, resistance or power and get the other two, with the V, I, R and P formulas shown.
Voltage Divider Calculator
Calculate the output of a resistive voltage divider. Enter the input voltage and two resistors to get Vout, the current and the divider ratio instantly.
555 Timer Calculator
Calculate 555 timer astable frequency, period, high and low times and duty cycle from R1, R2 and the timing capacitor. Free oscillator design helper.
Absolute Humidity Calculator
Calculate absolute humidity in grams of water vapor per cubic meter from air temperature and relative humidity. Fast, free and works in your browser.
Allele Frequency Calculator
Find allele frequencies from genotype counts. Enter the number of AA, Aa and aa individuals to get the A and a allele frequencies and allele totals.