Electrical Formulas

To Find Direct Current Alternating Current
Single Phase Two-Phase* Four-Wire Three Phase
Amperes when Horsepower is known HP x 746
E x EFF		 HP x 746
E x EFF x PF x 2		 HP x 746
2 x E x EFF x PF		 HP x 746
E x EFF x PF x 1.73
Amperes when Kilowatts are known KW x 1000
E		 KW x 1000
E x PF		 KW x 1000
2 x E x PF		 KW x 1000
E x PF x 1.73
Amperes when "KVA" is known KVA x 1000
E		 KVA x 1000
KVA x 1000
E x 1.73
Kilowatts E x I
1000		 E x I x PF
1000		 I x E x 2 x PF
1000		 E x I x 1.73 x PF
1000
Kilovolt-Amperes "KVA" - I x E
1000		 I x E x 2
1000		 E x I x 1.73
1000
Horsepower (Output) E x I x EFF
746		 E x I x EFF x PF
746		 I x E x 2 x EFF x PF
746		 E x I x EFF x PF x 1.73
746

E = Voltage
I = Amps
PF = Power Factor
EFF = Efficiency
HP = Horsepower

Note: Direct current formulas do not use (PF, 2, or 1.73)

  • Single phase formulas do not use (2 or 1.73)
  • Two phase-four wire formulas do not use (1.73)
  • Three phase formulas do not use (2)
  • * For three-wire, two phase circuits the current in the common conductor is 1.41 times that in either of the other two conductors.