# Power in DC and AC Circuits

##### Formulas of Power in DC, AC Single Phase and AC Three Phase Circuits

Back to basic, below are the simple Power formulas for Single Phase AC Circuit, Three Phase AC Circuits and DC Circuits. You can easily find electric power in watts by using the following power formulas in electric circuits.

##### Power Formulas in DC Circuits

P = V x I

P = I2 x R

P = V2 / R

Where:

P = Power in Watts

V = Voltage in Volts

I = Current in Amperes

R = Resistance in Ohms (Ω)

##### Power Formulas in Single Phase AC Circuits

P = V x I x Cos Ф

P = I2 x R x Cos Ф

P = V2 / 2 (Cos Ф)

Where:

P = Power in Watts

V = Voltage in Volts

I = Current in Amperes

R = Resistance in Ohms (Ω)

Cos Ф = Power Factor

##### Power Formulas in Three Phase AC Circuits

P = √3 x VL x IL x Cos Ф

P = 3 x VPh x IPh x Cos Ф

P = 3 x I2 x R x Cos Ф

P = 3 (V2 / R) x Cos Ф

Where:

P = Power in Watts

V = Voltage in Volts

I = Current in Amperes

R = Resistance in Ohms (Ω)

Cos Ф = Power Factor