Single & Three Phase Power Calculator
Find AC power or current from voltage, power factor and phase.
Results
Active input power
- Apparent power
- 6.58 kVA
- Line current
- 10 A
- Three-phase: use RMS line-to-line voltage and line current; the load is assumed balanced.
This is a general AC estimate; three-phase calculations assume a balanced system. Equipment selection must separately account for manufacturer ratings, starting current and load characteristics.
Formula · How it works
Formula
S = k × V × I; P = S × PFI = P / (k × V × PF)I = Pout / (k × V × PF × η)k = 1 for single phase and √3 for balanced three-phase. P uses watts, S uses VA and η is a fraction. PF = P/S; it must be greater than zero and no more than one for this calculator.
Worked example
A balanced three-phase load at 380 V line-to-line, 10 A and PF = 1 uses P = √3 × 380 × 10 = 6,581.793 W ≈ 6.58 kW. Apparent power is 6.58 kVA.
How it works
Select the supply phase and the quantity to calculate. Electrical input power already includes motor losses. When starting from motor shaft output, input power is output power divided by efficiency. The hp equivalent expresses a unit conversion and does not imply that all electrical input becomes shaft output.
Common questions
Which voltage should I enter for three-phase?
Use the RMS line-to-line voltage, such as 380 V or 400 V, with line current. Do not substitute line-to-neutral voltage in the √3 formula.
When should I include motor efficiency?
Use efficiency when calculating current from mechanical shaft output. Do not divide again by motor efficiency when the supplied value is already electrical input power.