Load Power Factor Calculator

Calculator

Method *

Choose the inputs you already have.

System

Affects apparent power in V–I methods.

Load type

Sets the sign of reactive power.

Real power P (kW) *

Real (active) power consumed by the load.

Apparent power S (kVA)

Used when method is P and S.

Reactive power Q (kVAr)

Used when method is P and Q or V–I–Q.

Voltage V (V)

Line voltage for three-phase inputs.

Current I (A)

RMS current drawn by the load.

Optional: power factor correction estimate

Enter a higher target PF to estimate required capacitor size for lagging loads.

Target PF (0–1)

Used only when target PF is greater.

Frequency (Hz)

Needed for capacitance in µF.

Voltage for correction (V)

Line voltage for three-phase connections.

Connection

Used for per-phase capacitance estimate.

Quick tip

If your load is inductive, select “Lagging”.

Correction sizing is shown when target PF is higher than current PF.

Example data

Scenario	Inputs	Expected PF	Notes
Workshop motor	P=12 kW, S=15 kVA, Lagging	0.80	Q ≈ 9 kVAr
HVAC unit	P=8 kW, Q=6 kVAr, Lagging	0.80	S=10 kVA
3φ pump	V=400 V, I=25 A, P=13 kW	≈0.75	Uses √3·V·I

Values are rounded for illustration.

Formula used

Power factor: PF = P / S
Apparent power: S = √(P² + Q²)
Reactive power (magnitude): |Q| = √(S² − P²)
Phase angle: φ = arccos(|PF|) (in degrees)
From voltage and current:
- Single-phase: S(kVA)= V·I / 1000
- Three-phase: S(kVA)= √3·V_line·I / 1000
Correction kVAr (lagging loads): Qc = P·(tanφ₁ − tanφ₂)
Capacitance estimate:
- Single-phase: C = (Qc·1000)/(2πf·V²)
- Three-phase delta: C = (Qc·1000)/(3·2πf·V_LL²)
- Three-phase star: uses V_ph=V_LL/√3 per phase.

Sign convention: lagging Q is positive, leading Q is negative.

How to use this calculator

Select a method that matches your available measurements.
Choose single-phase or three-phase, then pick load type.
Enter the required values, then press Submit.
Review PF, φ, P, Q, and S in the Results panel.
Optionally set a target PF to estimate correction kVAr and µF.
Use the download buttons to export CSV or PDF files.

FAQs

1) What does power factor indicate?

It shows how effectively electrical power becomes useful work. A lower PF means more current for the same kW, increasing losses and voltage drop.

2) Why is lagging power factor common?

Most motors and transformers are inductive, so current lags voltage. This produces positive reactive power and reduces PF compared with purely resistive loads.

3) Can power factor be greater than 1?

No. PF magnitude is between 0 and 1. If you see a value above 1, recheck units, phase selection, and whether P, Q, or S were entered correctly.

4) What is the difference between kW, kVA, and kVAr?

kW is real power used for work. kVAr is reactive power that oscillates in fields. kVA is apparent power, combining both as the total demand on the supply.

5) How does three-phase affect calculations?

For V–I based apparent power, three-phase uses √3·V_line·I. Enter line-to-line voltage and RMS current to estimate kVA and PF properly.

6) When should I use the correction estimate?

Use it when your load is inductive and you want a higher PF, such as 0.95. It estimates the capacitor kVAr needed to reduce reactive power.

7) Is the capacitance value exact for real installations?

It is an estimate. Real systems consider harmonics, temperature, capacitor tolerances, and switching steps. Confirm with equipment datasheets and qualified engineering review.