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Elliott Electric Supply

Electrical Formulae for Calculating Amps, Horsepower, Kilowatts, & KVA


Use the chart in this calculation guide to find the formula you need according to the measure you will calculate.

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
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
2 x E
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 formulae 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 the current in either of the other two conductors.