Real Power Calculator
Calculate the real power actually converted into useful work in an AC circuit.
About Real Power Calculator
Real power is what the energy meter records and what performs work. The √3 factor appears in three-phase because line voltage exceeds phase voltage by that ratio in a star connection. Forgetting the √3 factor understates three-phase power by 42 per cent, which is a common and expensive sizing error.
Formula
Real Power
P = V I cos φ single phase; P = √3 V I cos φ three phase
- √3
- Factor relating line and phase quantities in a balanced three-phase system
Worked example
With the default values below, Real Power Calculator returns Real Power of 12.4708. Change any input above and every figure here is recalculated in your browser.
Inputs used
- RMS voltageminimum 0 V
- 400 V
- RMS currentminimum 0 A
- 20 A
- Power factoraccepts 0.01–1
- 0.9
- Phasesone of Single phase, Three phase
- Three phase
Results
- Real Power
- 12.4708 kW
- Real Power
- 12,470.77 W
- Apparent Power
- 13.8564 kVA
- Annual Energy at Continuous Duty
- 109,244 kWh
- Equivalent Mechanical Power
- 16.724 hp
Step by step
- 1Values used
- 2Real Power
- 3Real Power= 12.4708 kW
- 4Real Power= 12,470.77 W
- 5Apparent Power= 13.8564 kVA
- 6Annual Energy at Continuous Duty= 109,244 kWh
- 7Equivalent Mechanical Power= 16.724 hp
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Real Power calculated?
P = V I cos φ single phase; P = √3 V I cos φ three phase Real power is what the energy meter records and what performs work. The √3 factor appears in three-phase because line voltage exceeds phase voltage by that ratio in a star connection.
Why does Real Power matter?
Forgetting the √3 factor understates three-phase power by 42 per cent, which is a common and expensive sizing error.
What values do I need to enter?
This calculator takes 4 inputs: RMS voltage, RMS current, Power factor, Phases. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.