Power Factor Calculator

Calculate power factor (PF) from real power, voltage, and current for single-phase or three-phase circuits — or work backward from a known real and apparent power reading off a utility bill or nameplate. This calculator solves the full power triangle, returning your phase angle, apparent power (kVA), and reactive power (kVAR) alongside the power factor itself, then sizes the exact correction capacitor needed to reach a target power factor such as the 0.95 most utilities require to avoid a low-PF penalty. A live power-triangle diagram illustrates how real, reactive, and apparent power relate for your numbers, and an optional Utility Penalty & Payback estimate shows how much a correction capacitor bank could save on your bill and how long it would take to pay for itself. Every result shows the formula used with your values substituted in, and the full page — diagram included — prints exactly as it appears on screen for job-site or client documentation.

Use Volts & Amps if you have a meter reading of real power, voltage, and current. Use Real & Apparent Power if you already know your power in kW and kVA from a utility bill or equipment nameplate.

Need standard capacitor values or physical sizing details for the correction capacitor sized below? Use the Capacitor Calculator →

Formula: PF = (Real Power × 1,000) ÷ (Voltage × Current), with a √3 (line-to-line) or 3× (line-to-neutral) multiplier applied automatically for three-phase.

Real Power (kW)

Voltage (V) — per phase

Current (A)

Frequency (Hz) — for capacitor sizing

Target Power Factor — default 0.95

Utility Penalty Threshold PF — default 0.90

Penalty Rate ($/kVAR/mo) — optional, for savings estimate

Capacitor Bank Cost ($) — optional, for payback estimate

Power Factor

—

Phase Angle (θ)

—

degrees

Apparent Power

—

kVA

Reactive Power

—

kVAR

Formula: —

Correction Capacitor Sizing

Required Correction

—

kVAR

Capacitor Size

—

µF

Formula: —

🎁 Bonus: Utility Penalty & Payback

Estimate only — actual utility tariffs vary; verify against your rate schedule.

Excess Billable kVAR

—

kVAR

Est. Monthly Penalty Avoided

—

USD / month

Simple Payback

—

months

Power Triangle

Real power (P), reactive power (Q), and apparent power (S) drawn to scale for your result, with the phase angle (θ) between P and S.

Results are for reference and estimation only. Verify all values before use in any electrical design or correction decision. See full disclaimer below.

How to Use the Power Factor Calculator

Choose Your Input Method

Select Volts & Amps if you have a meter reading of real power, voltage, and current, or Real & Apparent Power if you already know your power in kW and kVA from a utility bill or nameplate.

Enter Your Values

For Volts & Amps, also choose Single-Phase or Three-Phase and, for three-phase, Line-to-Line or Line-to-Neutral voltage. Add your Target Power Factor and Frequency for capacitor sizing, and optionally your utility's penalty threshold and rate for a savings estimate.

Click Calculate

See your power factor, phase angle, apparent and reactive power, the power triangle, and the exact capacitor size needed to reach your target power factor, with the formula substituted with your numbers.

Check the Reference Table and Print

Expand the Power Factor Quality Reference table to see how your result compares to industry bands, or use Print to capture the results — power triangle included — exactly as they appear on screen for documentation.

Power Factor Quality Reference

How your calculated power factor compares to standard industry bands. Most utilities set their penalty threshold around 0.90.

Band	PF Range	What It Means
Unity	1.00	All supplied power is doing useful work — the ideal case.
Good	0.95 – 0.99	Above most utility requirements; no penalty expected.
Average	0.80 – 0.95	Typical uncorrected industrial load; correction often pays for itself.
Poor	Below 0.80	Likely incurring utility penalties; correction strongly recommended.

Bands are general industry guidance. Confirm your own utility's exact penalty threshold and rate structure on your tariff sheet.

Frequently Asked Questions

What is power factor and why does it matter?

Power factor (PF) is the ratio of real power (the power that performs useful work, in kW) to apparent power (the total power supplied to the circuit, in kVA). It ranges from 0 to 1, where 1.0 means every unit of power delivered is doing useful work. A low power factor means the system draws more current than necessary to do the same work, which increases line losses, reduces available system capacity, and can trigger penalty charges from your utility.

How do I calculate power factor from voltage, current, and real power?

For a single-phase circuit, PF = (Real Power in kW × 1,000) ÷ (Voltage × Current). For a three-phase circuit, divide by √3 × line-to-line voltage × current instead of just V × I, or by 3 × line-to-neutral voltage × current if you're using line-to-neutral voltage. Enter your values into the Volts & Amps tab above and the calculator applies the correct formula automatically based on the phase and voltage type you select.

How do I size a capacitor to correct my power factor?

First find your existing phase angle from your current power factor, then find the phase angle at your target power factor. The required correction, Qc, equals your real power multiplied by the difference between the tangents of those two angles. That reactive power is then converted to microfarads using your system voltage and frequency. The Target Power Factor and Frequency fields above calculate this automatically.

What's considered a good power factor, and what's the utility penalty threshold?

A power factor of 0.95 or higher is generally considered good, with 1.0 being ideal. Most utilities set a penalty threshold around 0.90 — falling below it typically means a surcharge on your bill for the extra reactive power the utility has to supply. Enter your utility's specific threshold and rate in the Penalty & Payback fields above for an estimate of potential savings from correction — confirm the exact figures on your own tariff sheet.

How do single-phase and three-phase power factor calculations differ?

The underlying ratio, PF = real power ÷ apparent power, is the same in both cases. What differs is how apparent power is derived from voltage and current: three-phase apparent power includes a √3 (or 3, for line-to-neutral voltage) multiplier that single-phase circuits don't have, since three-phase systems distribute power across three conductors instead of two. Selecting the correct phase and voltage type above ensures the right multiplier is applied. If you already know both P and S directly, use the Real & Apparent Power tab instead — no phase selection needed.

Power Factor Calculator

How to Use the Power Factor Calculator

Power Factor Quality Reference

Frequently Asked Questions

What is power factor and why does it matter?

How do I calculate power factor from voltage, current, and real power?

How do I size a capacitor to correct my power factor?

What's considered a good power factor, and what's the utility penalty threshold?

How do single-phase and three-phase power factor calculations differ?

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