Power Factor Calculator

See how active power factor correction reshapes the input current waveform. Adjust the phase angle and toggle PFC on or off — the widget plots voltage, current, and instantaneous power while reporting PF, true power, and apparent power live.

V_rms: 230 VP_load: 250 W

THD_i (uncorrected): 150 %

φ (displacement): 0 °

Waveforms normalized for shape comparison — voltage and current amplitudes are not to the same scale

Power Factor

0.555

Displacement PF

1.000

\small \cos(0^\circ) = 1.000

Distortion PF

0.555

\small \tfrac{1}{\sqrt{1+1.50^2}} = 0.555

Combined Power Factor

\small PF = \cos\varphi \cdot \tfrac{1}{\sqrt{1+THD_i^2}} = 1.000 \times 0.555 = 0.555

THD_i = 150% = 1.50 (decimal)

$I_{rms}$ (drawn from mains)

1.96 A

$S$ (Apparent power)

450.7 VA

$P$ (Real power)

250.0 W

Extra current wasted

44.5% of apparent power is non-useful

Quick experiments

Default diode bridge. With the default settings the power factor reads around 0.55 — a typical uncompensated rectifier load.
Toggle PFC on. Enable active PFC and watch the current snap into phase with voltage, pushing PF close to unity.
Phase lag without PFC. Set φ = 30° with PFC off — the displacement drops PF to cos 30° ≈ 0.87, and the power waveform dips negative each cycle.

Power factor in AC circuits

Power factor (PF) is the ratio of real power P (watts) to apparent power S (volt-amperes): PF = P / S = cos(φ), where φ is the phase angle between voltage and current. A PF of 1.0 means all supplied energy does useful work; lower PF means the grid must supply more current for the same useful power.

Real, reactive, and apparent power

P (W): real power — does actual work (heat, motion, light).
Q (VAR): reactive power — stored and returned by inductors/capacitors; does no net work but loads cables and transformers.
S (VA): apparent power — S = √(P² + Q²); what the generator and cables must provide.

Power factor correction (PFC)

Adding capacitors in parallel with inductive loads (motors, fluorescent ballasts) cancels reactive current and raises PF toward 1.0. Industrial users are charged by utilities for reactive power when PF drops below 0.95. Switched-mode power supplies use active PFC circuits to maintain near-unity PF.

Learn more → Power Factor Correction — Learn