About the Amps to kW Calculator
Electricity supply and generator sizes are given in kilowatts, while breakers, meters and clamp testers show amps. This calculator converts amps to kilowatts by multiplying the current by the voltage, then by the power factor for AC and by the square root of three for three-phase supplies, and dividing by 1,000. It also shows the mechanical horsepower equivalent and the apparent power in kVA, which are handy when you are sizing motors, generators and transformers. The default values show a typical three-phase workshop supply.
Updated October 2026
How to use the Amps to kW Calculator
- 1Choose DC, single-phase or three-phase.
- 2Enter the current in amps.
- 3Enter the voltage between lines for three-phase supplies.
- 4Enter the power factor for AC loads.
- 5Read the power in kilowatts, with horsepower and kVA below.
Common three-phase examples
- 16 A at 400 V, power factor 1: about 11 kW.
- 32 A at 400 V, power factor 1: about 22 kW.
- 63 A at 400 V, power factor 0.9: about 39 kW.
- 100 A at 415 V, power factor 0.85: about 61 kW.
- 200 A at 480 V, power factor 0.8: about 133 kW.
Why the units differ
Watts are used for the real work a device does, such as heat or shaft power. Amps describe how much charge flows, which is what heats the cables and trips the breakers. Because the voltage links them, the same amps can mean very different power on different systems, and reading only one of the numbers can give a misleading idea of the load.
One more point is worth remembering: the kilowatts you pay for on a bill are real power, not apparent power. A site drawing 100 amps per phase at 400 volts with a poor power factor of 0.7 uses about 48 kW of real power, while the same current at a power factor of 0.95 would be roughly 66 kW of useful work. Some suppliers charge extra for a low power factor in industrial premises, so knowing both figures helps you judge whether correction equipment would pay for itself.
Other tools to use
The kW to Amps Calculator goes the other way, the kVA to kW Calculator converts between apparent and real power, the Horsepower Calculator handles engine and motor sizes and the kWh Calculator turns power into energy use over time. The Electricity Bill Calculator works out running costs.
Features
- Kilowatts from amps and volts
- Single-phase, three-phase and DC
- Power factor input
- Horsepower and kVA shown too
- Large and small values supported
- Runs in your browser
Frequently asked questions
What is the formula for amps to kW?
For single-phase AC, kW equals amps times volts times power factor divided by 1,000. For three-phase it is amps times line voltage times 1.732 times power factor divided by 1,000. For DC, leave out the power factor.
How many kW is 100 amps?
It depends on voltage. At 230 volts single-phase with a power factor of 1, 100 amps is 23 kW. At 400 volts three-phase with a power factor of 0.9, it is about 62.4 kW.
What power factor should I use?
Use the value on the equipment label if there is one. Resistive loads such as heaters are close to 1, induction motors typically 0.8 to 0.9 when well loaded, and lightly loaded motors can be much lower. If unsure, 0.8 is a cautious guess.
Is kW the same as kVA?
No. kW is the real power doing work and kVA is the apparent power the supply must provide. They match only when the power factor is 1. Generators are rated in kVA, so a 100 kVA unit at 0.8 power factor supplies 80 kW.
How do I convert kW to horsepower?
Divide kilowatts by 0.7457 to get mechanical horsepower. The calculator shows this beside the answer, using the figure for real power.
Can I use it for an electric vehicle charger?
Yes. A 32 amp single-phase charger at 230 volts is about 7.4 kW, and a 32 amp three-phase charger at 400 volts is about 22 kW, assuming a power factor near 1.