Electrical Formulas

E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP = Horsepower

AC/DC Formulas

To Find Direct Current AC / 1phase
115v or 120v		 AC / 1phase
208,230, or 240v		 AC 3 phase
All Voltages
Amps when
Horsepower is Known		 HP x 746
E x Eff		 HP x 746
E x Eff X PF		 HP x 746
E x Eff x PF		 HP x 746
1.73 x E x Eff x PF
Amps when
Kilowatts is known		 kW x 1000
E		 kW x 1000
E x PF		 kW x 1000
E x PF		 kW x 1000
1.73 x E x PF
Amps when
kVA is known		 kVA x 1000
E		 kVA x 1000
E		 kVA x 1000
1.73 x E
Kilowatts I x E
1000		 I x E x PF
1000		 I x E x PF
1000		 I x E x 1.73 PF
1000
Kilovolt-Amps I x E
1000		 I x E
1000		 I x E x 1.73
1000
Horsepower
(output)		 I x E x Eff
746		 I x E x Eff x PF
746		 I x E x Eff x PF
746		 I x E x Eff x 1.73 x PF
746

Three Phase Values

For 208 volts x 1.732, use 360
For 230 volts x 1.732, use 398
For 240 volts x 1.732, use 416
For 440 volts x 1.732, use 762
For 460 volts x 1.732, use 797
For 480 Volts x 1.732, use 831
E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP = Horsepower

AC Efficiency and Power Factor Formulas

To Find Single Phase Three Phase
Efficiency 746 x HP
E x I x PF		 746 x HP
E x I x PF x 1.732
Power Factor Input Watts
V x A		 Input Watts
E x I x 1.732

Power – DC Circuits

Watts = E xI
Amps = W / E

Ohm’s Law / Power Formulas

P = watts

I = amps

R = ohms

E = Volts

Voltage Drop Formulas

Single Phase
(2 or 3 wire)
VD = 2 x K x I x L
CM
CM = 2K x L x I
VD
Three Phase
VD = 1.73 x K x I x L
CM
CM = 1.73 x K x L x I
VD
K = ohms per mil foot

(Copper = 12.9 at 75°)

(Alum = 21.2 at 75°)

Note: K value changes with temperature. See Code chapter 9, Table 8

L = Length of conductor in feet

I = Current in conductor (amperes)

CM = Circular mil area of conductor