Introduction
Power factor tells you how well an electrical system uses the power it draws. A power factor of 1.0 means all the power does useful work. A low power factor means energy is wasted, equipment runs harder, and electric bills go up. This power factor calculator helps you solve power triangle problems and find the right capacitor size to fix a poor power factor.
The tool has two modes. In Power Triangle mode, you enter any two known values, such as real power and power factor, and the calculator finds the rest, including reactive power (Q), apparent power (S), and the phase angle (φ). In Capacitor Correction mode, you enter your current power factor, your target power factor, and basic supply details like voltage and frequency. The calculator then tells you exactly how much capacitance you need to reach your goal.
Every result comes with a step-by-step solution and a chart so you can see how the power components relate to each other. This calculator gives you fast, accurate answers.
How to Use Our Power Factor Calculator
Enter your known power values or load details, and this calculator will find the missing values in your power triangle or tell you what size capacitor you need for power factor correction. It also shows a chart and a full step-by-step solution.
Calculation Mode: Pick "Power Triangle" to solve for unknown power values, or pick "Capacitor Correction" to find the capacitor size needed to improve your power factor.
Power Triangle Mode
Calculate From: Choose which two values you already know. Options include Real Power & Power Factor, Real Power & Reactive Power, Real Power & Apparent Power, Reactive Power & Apparent Power, or Apparent Power & Power Factor.
First Known Value: Type in the first value based on your selection. The label and unit will update to match your choice.
Second Known Value: Type in the second value. If this input asks for Power Factor, enter a number between 0 and 1.
Capacitor Correction Mode
Active Load Power (P): Enter your load's real power in kilowatts (kW).
Current Power Factor (PF₁): Enter your existing power factor. Use the number field or drag the slider. This must be less than 1.
Target Power Factor (PF₂): Enter the power factor you want to reach. This must be higher than your current power factor. Use the number field or the slider.
Supply Voltage (V): Enter your supply voltage in volts. Use line-to-line voltage for 3-phase systems or line-to-neutral voltage for single-phase systems.
Supply Frequency (f): Enter your supply frequency in hertz. Common values are 50 Hz or 60 Hz.
System Type: Select whether your system is 3-phase or single-phase. For 3-phase, the result shows capacitance per phase in a star connection.
Click Calculate to see your results, chart, and step-by-step solution. Click Reset to return all inputs to their default values.
What Is Power Factor?
Power factor tells you how well an electrical system uses the power it receives. It is a number between 0 and 1. A power factor of 1 means all the power delivered is being used to do real work. A low power factor means a lot of power is wasted. Most utility companies charge extra fees when your power factor drops too low, usually below 0.85.
The Power Triangle
In AC (alternating current) circuits, there are three types of power that form a right triangle:
- Real Power (P) – Measured in kilowatts (kW). This is the power that does actual work, like running motors or lighting rooms.
- Reactive Power (Q) – Measured in kilovolt-amperes reactive (kVAR). This power flows back and forth between the source and the load. It does no useful work, but motors and transformers need it to create magnetic fields.
- Apparent Power (S) – Measured in kilovolt-amperes (kVA). This is the total power the source must supply. It combines real and reactive power using the formula S = √(P² + Q²).
Power factor is simply real power divided by apparent power: PF = P ÷ S. The angle between real power and apparent power is called the phase angle (φ). A larger phase angle means a worse power factor.
Power Factor Correction with Capacitors
Inductive loads like motors, compressors, and fluorescent lights pull the power factor down. They create reactive power that wastes capacity on your electrical system. To fix this, you can add capacitors. Capacitors produce reactive power that cancels out the reactive power from inductive loads. This raises the power factor closer to 1.
This calculator finds the exact capacitor size you need. You enter your real power, your current power factor, your target power factor, and your supply voltage and frequency. It then calculates the required capacitance in microfarads (μF). For three-phase systems, the result shows the capacitance per phase in a star (wye) connection.
Why Power Factor Matters
A poor power factor forces your electrical system to carry more current than necessary. This leads to higher electricity costs, larger cable sizes, and more heat in wires and equipment. Understanding voltage, current, and resistance relationships through Ohm's law helps explain why excess current causes these problems. Correcting power factor reduces energy costs, frees up capacity on transformers and generators, and lowers voltage drops across your system. Most facilities aim for a power factor of 0.95 or higher.