question

Please ask a question with enough information to be answered.

Its like asking, "how do I calculate the moon?". Well, what do you want to calculate? the weight of the moon? the speed of rotation? the amount of gamma rays reflecting from it's surface? how many little men are on the dark side? is it made of cheese? what kind of cheese... alright I'm kind of wandering off topic here....

Please elaborate on your question.

Hopefully this can help you find an answer to your question...

http://en.wikipedia.org/wiki/Volt-amperes_reactive

I assume that you want to calculate the kVAR of the capacitor required to correct the existing low power factor of a load to a desired target power factor. Right? If so, the capacitor kVAR required for improving the existing power factor (PF1) of a load to a target power factor (PF2) is;

kVAR (C) = kW [Tan (phi 1) - Tan (phi 2)]

where,

kVAR (C) = Capacitor kVAR required

kW = Active Power Rating of the Load(s) connected

phi 1 = angle of existinng Power Factor = Cos-1 (PF1)

phi 2 = angle of target power factor = Cos-1 (PF2)