Physics

Instant, private, and free

Power Factor Calculator.

Calculate power factor from real and apparent power.

On-device calculationNo signup
01

Set your values

Results update as you type.

Power factor: 0.8

Power factor

0.800000

Results update automatically as you type.

Use Cases

Assess Electrical Efficiency

Determine how efficiently your electrical equipment uses power. A low power factor indicates wasted energy and potential for improvement.

Example: A motor draws 5000 W real power and 6250 VA apparent power, giving a power factor of 0.8.

Size Power Correction Equipment

Use the power factor to decide if you need capacitors or other correction devices to improve efficiency and reduce utility penalties.

Example: If your facility has a power factor of 0.7, you might consider adding capacitors to raise it closer to 0.95.

Frequently Asked Questions

What is power factor and why is it important?
Power factor is the ratio of real power (W) to apparent power (VA). It indicates how effectively electrical power is converted into useful work. A higher power factor (closer to 1) means more efficient use of electricity, reducing energy losses and costs.
How do I use this calculator?
Enter the real power in watts (W) and the apparent power in volt-amperes (VA). The calculator will divide real power by apparent power to give you the power factor, a number between 0 and 1.
What does a power factor of 0.8 mean?
A power factor of 0.8 means that 80% of the apparent power is being converted into real work, while the remaining 20% is reactive power. This is a common value for many industrial loads.

Tips & Common Mistakes

Tips

  • Ensure both values are in the correct units: watts (W) for real power and volt-amperes (VA) for apparent power.
  • For accurate results, measure real and apparent power at the same point in your electrical system.
  • A power factor close to 1 is ideal; values below 0.9 may indicate inefficiency.
  • Use this calculator as a quick reference; for detailed analysis, consult an electrician or engineer.

Common Mistakes to Avoid

  • Using kilowatts (kW) and kilovolt-amperes (kVA) without converting to watts and volt-amperes. Always use consistent units.
  • Confusing real power with apparent power. Real power is the actual work done, while apparent power is the total power drawn from the source.
  • Assuming a power factor greater than 1 is possible. The power factor is always between 0 and 1.

Last updated: August 13, 2026