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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.