# Amperes on the Electrical Contractor's Test

An Ampere is a measurement of current and it is represented by the letter A.

To calculate Amperes in Direct Current systems, use:

Amperes = Horsepower x 745.7 / Volts x Efficiency

I = HP x 745.7 / V x Eff

I = HP x 745.7 / V x Eff

or

Amperes = KW x 1000 / Volts

I = KW x 1000 / V

I = KW x 1000 / V

To calculate amperes on single-phase, use:

Amperes = Watts / Volts x Power factor

I = P / V x Pf

I = P / V x Pf

Amperes = Horsepower x 745.7 / Volts

I = HP x 745.7 / V

I = HP x 745.7 / V

or

Amperes Kilowatts x 1000 / Volts x Power factor

I = KW x 1000 / V x Pf

I = KW x 1000 / V x Pf

To find Amperes on three-phase, use:

Amperes = Watts / Volts x Power factor x 1.73

I = P / V x Pf x 1.73

I = P / V x Pf x 1.73

or

Amperes = Horsepower x 745.7 / Volts x Efficiency x Power factor x 1.73

I = HP x 745.7 / V x Efficiency x Pf x 1.73

I = HP x 745.7 / V x Efficiency x Pf x 1.73

or

Amperes = Kilowatts x 1000 / Volts x Power factor x 1.73

I = KW x 1000 / V x Pf x 1.73

I = KW x 1000 / V x Pf x 1.73