Free Online calculation of electrical power and energy : formula and calculator

AC POWER calculator for single phase or 3-phase system (balanced load)

Active and apparent electrical power :

Energy calculation :

If you want to calculate energy associated to this active power, fill the time value below (number of hours and days the appliance is running) :

Formula to calculate power, current and voltage in single phase wiring :

        P=U*I*cosφ
        I=P/(U*cosφ)
        U=P/(I*cosφ)

P = power in watt (W)
U = voltage in Volt (V)
I = current in ampere (A)
cos φ = cosinus phi (without unit)

Formula to calculate power, current and voltage in three-phase wiring (balanced load, equal loads on each of three phases) :

        P=√3*U*I*cosφ
        I=P/(√3*U*cosφ)
        U=P/(√3*I*cosφ)

P = power in watt (W)
U = voltage in Volt (V)
I = current in ampere (A)
cos φ = cosinus phi (without unit)

Formula to calculate power, current and voltage in three-phase wiring (unbalanced load, different loads on each of three phases) :

        Pt=P1+P2+P3
        P1=V*I1*cosφ1
        I1=P1/(V*cosφ1)
        Same thing for each phase…
        V=P1/(I*cosφ1)

Pt = total power of the circuit in watt (W)
P1, P2, P3 = power of phase 1, phase 2 and phase 3 in watt (W)
V = voltage in Volt (V) exemple : V1=230 V in 400 V three-phases circuit
I1, I2, I3 = current of phase 1, phase 2 and phase 3 in ampere (A)
Cos φ1, Cos φ2 , Cos φ3 = cosinus phi of each phase (without unit)