kW to Amps: The Single Phase, Three Phase and DC Formula Chart
Converting kW to amps is the calculation that sizes cables, breakers, and switchgear, and getting it wrong is how a correctly specified generator ends up feeding an undersized distribution board. The relationships are fixed. What changes is whether the system is single phase, three phase, or direct current, and whether power factor and motor efficiency belong in the expression.
kW to Amps and Related Electrical Formulas
| To Determine | Single Phase | Three Phase | Direct Current |
| kVA | I x E / 1,000 | I x E x 1.732 / 1,000 | Not applicable |
| Kilowatts | I x E x PF / 1,000 | I x E x 1.732 x PF / 1,000 | I x E / 1,000 |
| Horsepower | I x E x EFF x PF / 746 | I x E x 1.732 x EFF x PF / 746 | I x E x EFF / 746 |
| Amperes (HP known) | HP x 746 / (E x EFF x PF) | HP x 746 / (1.732 x E x EFF x PF) | HP x 746 / (E x EFF) |
| Amperes (kW known) | kW x 1,000 / (E x PF) | kW x 1,000 / (1.732 x E x PF) | kW x 1,000 / E |
| Amperes (kVA known) | kVA x 1,000 / E | kVA x 1,000 / (1.732 x E) | Not applicable |
I is current in amperes, E is voltage in volts, PF is power factor, and EFF is motor efficiency as a decimal. Direct current has no kVA row because apparent power and real power are identical without a phase angle. In the three phase column, E is always the line to line voltage. Substituting a line to neutral figure is the most common error in this table.
Working the Calculation
A 500 kW three phase load at 400 V and 0.8 power factor draws 500,000 divided by (1.732 x 400 x 0.8), or 902 amperes. The same load expressed as apparent power is 625 kVA, and running that through the kVA row returns 902 amperes again, which is a useful check that the power factor has been applied once rather than twice.
Nine hundred amperes is the number that sizes the cable, the breaker, and the busbar. It is also why medium voltage distribution exists: the identical 500 kW at 11 kV draws 32.8 amperes. Our power plant engineering team runs this on every EPC construction project before conductor selection.
Frequently Asked Questions
How do I convert kW to amps on a three phase system?
Multiply kW by 1,000, then divide by 1.732 times the voltage times the power factor. For 500 kW at 400 V and 0.8 power factor, the answer is 902 amperes.
How do I convert kVA to amps?
Divide kVA by 1,000 and by the voltage, and for three phase also by 1.732. No power factor term applies, because kVA is already apparent power.
Should I use 1.73 or 1.732?
Use 1.732. Both approximate the square root of three, but 1.73 introduces about 0.12 percent of error, and mixing the two within one calculation sheet is how small discrepancies get argued about later.
Why does horsepower need an efficiency term?
Because horsepower is mechanical output at the shaft while amperes measure electrical input. Motor efficiency accounts for the losses between the two.
Every kW to amps calculation on a project should be traceable to the same sheet. USP&E Global has delivered 150+ projects across 35+ countries, with equipment across the full range in our live inventory including diesel generating sets. Power sector and transmission data is published by the U.S. Energy Information Administration, the World Bank, and the IFC.
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