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.