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Electrical Formulas

by Brandy McNeil
in Calculations
February 26, 2017
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.