Power Factor Calculator
Calculate power factor from real and apparent power, and the phase angle it implies.
About Power Factor Calculator
Power factor is the fraction of apparent power doing useful work. Below about 0.9 most utilities apply penalties, because the reactive current still has to be generated and transmitted. Power factor correction is one of the shortest-payback electrical improvements available, often under two years where penalties apply.
Formula
Power Factor
Power factor = real power ÷ apparent power = cos φ
- φ
- Phase angle between voltage and current
Worked example
With the default values below, Power Factor Calculator returns Power Factor of 0.8000. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Real powerminimum 0 kW
- 8 kW
- Apparent powerminimum 0.001 kVA
- 10 kVA
Results
- Power Factor
- 0.8000
- Phase Angle
- 36.870 degrees
- Reactive Power
- 6.0000 kVAR
- Rating
- Poor — correction is usually worthwhile
- Capacity Not Doing Useful Work
- 20.00%
Step by step
- 1Values used
- 2Power Factor
- 3Power Factor= 0.8000
- 4Phase Angle= 36.870 degrees
- 5Reactive Power= 6.0000 kVAR
- 6Rating= Poor — correction is usually worthwhile
- 7Capacity Not Doing Useful Work= 20.00
Assumptions and limits
- The result is derived only from the 2 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 Power Factor calculated?
Power factor = real power ÷ apparent power = cos φ Power factor is the fraction of apparent power doing useful work. Below about 0.9 most utilities apply penalties, because the reactive current still has to be generated and transmitted.
Why does Power Factor matter?
Power factor correction is one of the shortest-payback electrical improvements available, often under two years where penalties apply.
What values do I need to enter?
This calculator takes 2 inputs: Real power, Apparent power. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.