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.