Power Factor Calculator - Power Triangle, Capacitor Sizing

Q: What is a good power factor number?

A power factor of 0.95 or higher is considered excellent. Between 0.85 and 0.95 is good. Between 0.70 and 0.85 is fair, and anything below 0.70 is poor. Most utility companies want you to stay above 0.85 to avoid penalty charges.

Q: What is the difference between kW, kVA, and kVAR?

kW (kilowatts) is real power — the power that does useful work like running a motor. kVA (kilovolt-amperes) is apparent power — the total power your source must deliver. kVAR (kilovolt-amperes reactive) is reactive power — the power that flows back and forth without doing work. They are related by the formula: S² = P² + Q², or kVA² = kW² + kVAR².

Q: Can power factor be greater than 1?

No. Power factor is always a number between 0 and 1 . It equals real power divided by apparent power (PF = P ÷ S). Since real power can never be larger than apparent power, the power factor can never go above 1.

Q: Should I use line-to-line or line-to-neutral voltage?

For 3-phase systems , enter the line-to-line voltage (for example, 400 V or 480 V). For single-phase systems , enter the line-to-neutral voltage (for example, 230 V or 120 V). Using the wrong voltage type will give you the wrong capacitor size.

Q: Why is my target power factor not accepted?

The target power factor (PF₂) must be higher than your current power factor (PF₁). It must also be between 0 and 1. If your current PF is 0.85, your target must be above 0.85. Setting the target to 1.0 (unity) is allowed but may require a very large capacitor.

Q: What happens if I set the target power factor to 1.0?

Setting the target to 1.0 means you want to remove all reactive power . This gives the largest capacitor size. In practice, most facilities aim for 0.95 to 0.98 because reaching exactly 1.0 requires a much bigger and more expensive capacitor bank, and slight overcorrection can cause problems.

Q: Does this calculator work for both 50 Hz and 60 Hz systems?

Yes. Enter 50 Hz if you are in regions like Europe, Asia, or Africa. Enter 60 Hz if you are in North America or parts of South America. The frequency affects the capacitor size — a higher frequency means a smaller capacitor is needed for the same correction.

PF Calculator

Updated Jul 9, 2026 By Jehan Wadia

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. Whether you are a student learning about AC circuits or an engineer sizing a capacitor bank, 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). If you need to convert between power units, our power calculator can help.

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. You can use our voltage drop calculator to check voltage levels across your conductors.

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. Our 3 phase power calculator can help with additional three-phase calculations.

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. You can explore the relationship between watts and amperes using our watts to amps calculator.
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). Our kVA calculator can help you work with apparent power in different circuit configurations.

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. Our capacitor calculator provides additional tools for working with capacitance values and energy storage.

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. If you need to convert between kVA and amperes for your system, try our kVA to amps calculator.

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.

Formulas used

Apparent Power (Power Triangle)

S = \sqrt{P^2 + Q^2}

Power Factor

PF = \frac{P}{S}

Phase Angle

\varphi = \arccos(PF)

Reactive Power from Apparent Power and Phase Angle

Q = S \times \sin(\varphi)

Required Reactive Compensation

Q_c = P \left( \tan \varphi_1 - \tan \varphi_2 \right)

Correction Capacitance

C = \frac{Q_c}{2 \pi f V^2}

Frequently asked questions

What is a good power factor number?

A power factor of 0.95 or higher is considered excellent. Between 0.85 and 0.95 is good. Between 0.70 and 0.85 is fair, and anything below 0.70 is poor. Most utility companies want you to stay above 0.85 to avoid penalty charges.

What is the difference between kW, kVA, and kVAR?

kW (kilowatts) is real power — the power that does useful work like running a motor. kVA (kilovolt-amperes) is apparent power — the total power your source must deliver. kVAR (kilovolt-amperes reactive) is reactive power — the power that flows back and forth without doing work. They are related by the formula: S² = P² + Q², or kVA² = kW² + kVAR².

What does the phase angle mean?

The phase angle (φ) is the angle between voltage and current in an AC circuit. When the phase angle is 0°, voltage and current are perfectly in sync and the power factor is 1.0. As the phase angle gets larger, more reactive power is present and the power factor drops. You can find the phase angle with the formula φ = arccos(PF).

Can power factor be greater than 1?

No. Power factor is always a number between 0 and 1. It equals real power divided by apparent power (PF = P ÷ S). Since real power can never be larger than apparent power, the power factor can never go above 1.

Should I use line-to-line or line-to-neutral voltage?

For 3-phase systems, enter the line-to-line voltage (for example, 400 V or 480 V). For single-phase systems, enter the line-to-neutral voltage (for example, 230 V or 120 V). Using the wrong voltage type will give you the wrong capacitor size.

What does per phase mean in the capacitor result?

When you select 3-phase, the calculator gives the capacitance needed for one phase in a star (wye) connection. Your total capacitor bank uses three of these capacitors — one on each phase. So the total capacitance is 3 times the displayed value.

Why is my target power factor not accepted?

The target power factor (PF₂) must be higher than your current power factor (PF₁). It must also be between 0 and 1. If your current PF is 0.85, your target must be above 0.85. Setting the target to 1.0 (unity) is allowed but may require a very large capacitor.

How do I find my current power factor?

You can find your current power factor in several ways:

Check your electricity bill — many utilities list it.
Use a power factor meter or power quality analyzer.
If you know your real power (kW) and apparent power (kVA), divide kW by kVA to get the power factor.

What happens if I set the target power factor to 1.0?

Setting the target to 1.0 means you want to remove all reactive power. This gives the largest capacitor size. In practice, most facilities aim for 0.95 to 0.98 because reaching exactly 1.0 requires a much bigger and more expensive capacitor bank, and slight overcorrection can cause problems.

Does this calculator work for both 50 Hz and 60 Hz systems?

Yes. Enter 50 Hz if you are in regions like Europe, Asia, or Africa. Enter 60 Hz if you are in North America or parts of South America. The frequency affects the capacitor size — a higher frequency means a smaller capacitor is needed for the same correction.

What is the formula for calculating correction capacitance?

The formula is:
C = Qc ÷ (2π × f × V²)
Where Qc is the reactive power to be compensated (in VAR), f is the supply frequency (in Hz), and V is the supply voltage (in volts). The calculator converts the result to microfarads (μF) for you.

Can I use this calculator for leading power factor?

This calculator assumes a lagging power factor, which is the most common case in systems with motors, transformers, and other inductive loads. It does not handle leading power factor scenarios where the system is already over-corrected by too much capacitance.

How much money can power factor correction save?

Savings depend on your utility's rate structure, but correcting a poor power factor can reduce electricity bills by 10% to 30%. Many utilities charge reactive power penalties when your power factor drops below 0.85 or 0.90. Raising your power factor eliminates these charges and also reduces current in your wiring, which lowers energy losses.

What is the difference between the two calculator modes?

Power Triangle mode solves for unknown power values. You enter any two known values (like real power and power factor) and it finds the rest, including reactive power, apparent power, and phase angle.

Capacitor Correction mode tells you what size capacitor you need to improve your power factor from a current value to a target value. You also enter voltage, frequency, and system type.

Why does the calculator show kVA reduction after correction?

When you improve the power factor, the apparent power (kVA) your system needs goes down even though the real power (kW) stays the same. This means your transformers, cables, and generators carry less current. The kVA reduction shows you how much spare capacity you free up by adding the correction capacitor.