How to use the kilowatt to amps calculator
- Choose whether to convert kilowatts to amps or amps to kilowatts.
- Enter the power or the current, and the voltage of the supply. For three phase, use the line to line voltage.
- Choose single phase AC, three phase AC or DC. For AC, enter the power factor. Use 1 for resistive loads such as heaters.
- Read the result and the table that shows the same power at other common voltages.
Formula
Single phase AC: amps = kW x 1,000 / (volts x power factor)
Three phase AC: amps = kW x 1,000 / (1.732 x volts x power factor)
DC: amps = kW x 1,000 / volts
Kilowatts from amps: the same formulas solved for power
1.732 is the square root of 3. Power factor is a number from above 0 to 1 that describes how much of the current does useful work.
A 3 kW load at 240 volts
On a single phase 240 V supply with a power factor of 1, the current is 3,000 / 240 = 12.5 A. The same 3 kW at 120 V draws 25 A, which is why higher voltage means lower current for the same power.
For a three phase load of 3 kW at 480 V with a power factor of 0.8, the current is 3,000 / (1.732 x 480 x 0.8) = 4.51 A. Going the other way, 12.5 A at 240 V single phase is 3 kW.
Power factor in plain terms
A resistive load such as a heater turns all the current into work, so its power factor is 1. Motors and some electronics draw more current than the work they do, and the power factor describes this. A lower power factor means more amps for the same kilowatts. Check the nameplate or specifications of the equipment.
The power factor field is hidden for DC because it does not apply there.
What this does not do
The amps shown are the current the load draws for the numbers you enter. They are not a wire size or a breaker rating. Sizing circuits depends on the type of load, how long it runs, temperature, wire length and your local electrical code, and should be done by a licensed electrician.
To see power, voltage, current and resistance together, try the Ohm law calculator. For running costs, use the electricity cost calculator, and for sizing a backup unit the generator wattage calculator.
Assumptions and limits
- The voltage and power factor are what you enter, and the load is steady.
- Three phase uses the line to line voltage and a balanced load.
- The table voltages are examples and not a list of what is available where you live.
- No wire, breaker or code sizing is done. Have a licensed electrician size circuits.
Frequently asked questions
How do you convert kW to amps?
Multiply the kilowatts by 1,000 and divide by the voltage times the power factor. For three phase, also multiply the voltage by 1.732. Three kW at 240 V single phase is 12.5 A.
What power factor should I use?
Use 1 for resistive loads such as heaters. For motors and other equipment, use the value on the nameplate or in the specifications. A lower power factor gives a higher current.
How do I convert amps to kW?
Multiply the amps by the voltage and the power factor, then divide by 1,000. For three phase, include 1.732. Choose Amps to kilowatts at the top of the tool.
Why does three phase need less current?
The same power is shared across three conductors, so each carries less. That is why the three phase formula has the 1.732 factor in the denominator.