# Calculation of reactive power factor correction

## Online calculator to size capacitors for power factor correction

Enter your own values in the white boxes, results are displayed in the green boxes.

Enter your actual value of the power factor PF or cos phi (cosφ) and the final value you want to reach via capacitors.
Fill also the apparent power value of your system in kVA.

 Initial value Final value Power factor or Cos phi Sin phi Tan phi Power (kVA) Power (kW)
Capacitor size (KVAr) :

## Formula for power factor correction : how to size capacitors ?

The equation to get the reactive power to improve a low power factor is :
Where :
Qc = Reactive power of capacitors
P = Active real power in kW
Tanφ 1 = initial phase angle without capacitors
Tanφ 2 = final phase angle with capacitors

How to get tan φ?
tan φ = acos(cosφ)
or
tan φ = sin φ/cos φ

## How to get Cos phi (or power factor) if you know only reactive energy and active energy value of a given period ?

The equation that gives the relation between real active energy and reactive energy for a given period is :
The equation that gives the power factor (cos phi) according to Tan phi is :