You can calculate the power factor by using the power triangle. You can use the principles of trigonometry. Here is what you get -
**P / S = cos φ**

Because power factor is equal to the ratio between real and apparent power,
Power factor = cos φ

Power Factor, PF = P(W)(V(V) × I(A))

Apparent Power, S(VA) = V(V) × I(A)

Reactive Power, Q(VAR) = √(|S(VA)|2 – P(W)2)

Power Factor, PF = P(W) (√3 × V(V) × I(A))

Apparent Power, S(VA) = √3 × V(V) × I(A)

Reactive Power, Q(VAR) = √(|S(VA)|2 – P(W)2)

Real power is the power which is consumed in an AC circuit. This is also known as true power or active power. The measurement unit for real power is watts.

- P = V I (In DC circuits)
- P = VI Cosθ (in Single phase AC Circuits)
- P = √3 VL IL Cosθ or (in Three Phase AC Circuits)
- P = 3 VPh IPh Cosθ
- P = √ (S2 – Q2) or
- P =√ (VA2 – VAR2) or Real or True power = √ (Apparent Power2– Reactive Power2) or
- kW = √ (kVA2 – kVAR2)

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