Power quality

Power Factor Calculator

PF = Watts ÷ Volt-Amps

Power Factor Calculator

Calculate power factor from real watts and apparent volt-amps.

Live Result
Formula-backed — instant professional result
POWER FACTOR
0 PF
Also equals 0 %
Formula used PF = Watts ÷ Volt-Amps Power factor shows how much apparent power becomes usable real power. 800W ÷ 1000VA = 0.80 PF

This calculator is an educational planning estimate. Verify safety-critical work with equipment nameplate data, local electrical code, and a qualified professional.

Calculate power factor from watts and VA. Find kVAR for capacitor sizing. Supports single-phase and 3-phase AC power calculations.

AC power quality

Power triangle clarity

Calculate power factor from watts and VA. Find kVAR for capacitor sizing. Supports single-phase and 3-phase AC power calculations.

AC/DC single-phase formula-first page-specific visual

Power Factor Calculator — Real, Apparent & Reactive Power | Ampstowatt Guide

Real vs apparent power

Watts, VA, kVA, and power factor shown as one relationship

These conversions depend on the difference between real and apparent power, so the power triangle makes the formula easier to trust.

Formula PF = Watts / VA
Power Factor Calculator — Real, Apparent & Reactive Power | Ampstowatt technical circuit diagram A premium electrical diagram showing the main values and conversion flow for Power Factor Calculator — Real, Apparent & Reactive Power | Ampstowatt. Watts Reactive load kVA / VA PF = W / VA Generator sizing
Power Factor Calculator — Real, Apparent & Reactive Power | Ampstowatt Real vs apparent power with real formula values and planning checkpoints.

Quick answer

Use this calculator to separate real watts from apparent power.

AC equipment can draw VA or kVA that is higher than usable watts. Power factor explains the difference and is critical for generators, UPS systems, motors, and transformers.

PF = Watts / VA

Inputs to check before calculating

  • Use nameplate VA, kVA, or amperage where available.
  • Enter a realistic PF for motors, compressors, UPS systems, and generators.
  • Account for startup surge separately from running watts.
  • Compare real watts with equipment output ratings.

Example: real power vs apparent power

If equipment uses 800 W from 1,000 VA, the power factor is 0.80. Use that value when converting AC amps to watts or watts to amps for motors, HVAC, and generators.

Best use cases

  • Real vs apparent power
  • Current estimate
  • PF quality band
  • single-phase AC load planning with clear unit labels.

Common mistake to avoid

Do not treat kVA as kW unless the power factor is 1.00.

How to use the result

Use the result to avoid undersizing generators, UPS units, and AC power equipment.

Accuracy and safety note

Calculator output is a planning estimate. Final breaker sizing, wire gauge, derating, voltage-drop limits, equipment protection, and code compliance should be verified with manufacturer documentation and a qualified electrician or engineer.

For the broad formula, reference table, and breaker planning context, start with the main Amps to Watts Calculator.

Technical Diagram

Power Factor Calculator Formula Map

PF = W / VA

VA = apparent power, W = real power. Use the calculator on this page to change the inputs and verify the result before sizing equipment.

Apply This Knowledge

Start with the main conversion tool

Use these calculator pages to apply the concept to real current, voltage, watts, and power-factor problems.Amps to Watts Calculator

Methodology, Review Notes, and Sources

How this calculator works

The calculator applies Watt's law for DC and resistive loads, then adds power factor for AC loads and the 1.732 multiplier for balanced three-phase line-to-line calculations.

  • DC and resistive loads: W = A x V
  • Single-phase AC: W = A x V x PF
  • Three-phase AC: W = 1.732 x A x V x PF

Editorial review

Last reviewed: June 26, 2026. Ampstowatt.com is built around the amps to watts conversion — our core specialty. Content is maintained by the Ampstowatt editorial team and checked for formula consistency, unit labels, calculator behavior, and safety wording.

The page is an educational planning reference, not a licensed electrical design or inspection service.

Reference sources

FAQ

Power Factor FAQ

Fast answers before you use the calculator or compare formulas.

kVA What is the difference between kVA and kW?

kVA (kilovolt-amps) is apparent power — the total current × voltage product. kW (kilowatts) is real power — the portion that does useful work. The relationship is kW = kVA × Power Factor. A 10 kVA generator at PF 0.80 can deliver only 8 kW of real power. Always check whether equipment is rated in kVA or kW.

GEN How do I size a generator using kVA and power factor?

Calculate total real power (kW) needed, then divide by the generator power factor to get the required kVA rating: kVA = kW ÷ PF. For 12 kW of load with PF 0.80: kVA = 12 ÷ 0.80 = 15 kVA minimum generator. Add 20–25% for startup surges from motors and compressors.

GOOD What is a good power factor?

A power factor above 0.95 is excellent. 0.85–0.95 is acceptable for most installations. Below 0.85, utilities may charge power factor penalties. Below 0.70 indicates significant reactive power waste. Power factor correction capacitors can improve PF to 0.95+ by compensating for inductive loads.

VA How do I convert VA to watts?

Multiply VA by the power factor: Watts = VA × PF. A 1,500 VA UPS at PF 0.70 delivers 1,050 watts of real power. Modern UPS units often list both VA and watt ratings. If only VA is listed, assume PF 0.60–0.70 for older units and PF 0.90+ for newer models.

$ Why do utilities charge for low power factor?

Low power factor means the utility must supply extra current that does no useful work, heating transformers and transmission lines without generating revenue. Industrial customers with PF below 0.85–0.90 may face penalty surcharges of 1–2% per 0.01 PF below the threshold. Correction capacitors pay for themselves quickly.

VAR What is reactive power (kVAR)?

kVAR (kilovolt-amp reactive) is the reactive component of power — energy that oscillates between the source and inductive/capacitive loads without doing useful work. It combines with real power (kW) to form apparent power (kVA): kVA² = kW² + kVAR². Reducing kVAR through capacitor banks improves power factor.