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kW to Amps Calculator

Amps drawn by a load of known kW, volts and power factor.

How it is calculated

The tool applies the single-phase (or DC) relationship I = (P × 1000) ÷ (V × PF), where P is real power in kilowatts, V is the supply voltage in volts, PF is the power factor and I is the current in amps. If you leave the power factor empty it is taken as 1, which is right for resistive loads such as heaters. The power factor must be above 0 and no higher than 1, voltage must be above 0 and power cannot be negative; otherwise no result is shown. The tool has no phase selector and does not add a √3 term, so for a three-phase supply it overstates the current per line unless you account for that yourself. The answer is the running current, not the starting surge of motors.

Worked example

A 3 kW load runs on 230 V with a power factor of 0.9. Convert to watts: 3 × 1000 = 3,000 W. The denominator is 230 × 0.9 = 207. Current = 3,000 ÷ 207 = 14.49 A. Leaving the power factor blank would use 1, giving 3,000 ÷ 230 = 13.04 A, which shows how a lower power factor raises the current drawn for the same real power.

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Common mistakes

  • Using this result for a three-phase load. The formula is single-phase only, so divide by an extra √3 (about 1.732) yourself for line current at line-to-line voltage.
  • Typing the power factor as a percentage such as 90. It must be a value between 0 and 1; 90 returns no result.
  • Entering watts in the kW box. A 3000 W heater is 3 kW, and entering 3000 gives a thousandfold current.
  • Entering the wrong voltage, such as 400 V line-to-line for a single-phase 230 V circuit.
  • Choosing a breaker or cable at exactly the calculated amps. Continuous loads and inrush currents need margin, so rated capacity should be above the figure shown.

Sources

About this calculator

Electrical current draw depends on power, voltage, and — for AC circuits — power factor. This calculator uses the single-phase relationship current (A) = (power in kW × 1000) ÷ (voltage × power factor); if you leave the power factor blank it assumes 1. It has no phase setting, so for a balanced three-phase load enter the line-to-line voltage and divide the result by √3 (≈1.732) to get the current per line. Power factor, which ranges from 0 to 1, corrects for the fact that "real power" (kW) is only part of the total apparent power a circuit draws when the load isn't purely resistive.

Electricians, electrical engineers, and facility managers use this conversion to size circuit breakers, wiring gauge, and generators — undersizing wire for the actual current draw is a fire hazard, so codes require calculating amps from a device's rated kW before installation. It's also used when comparing appliance or motor nameplates that list power in kW against panel capacity rated in amps.

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Comments (1)

  • Editorial team

    Use the nameplate power factor for motors and fans; a motor labelled 0.8 draws noticeably more current than the kW alone suggests, which is why the field exists. For example 5 kW at 230 V and 0.9 gives 24.15 A, while the same load at 1 gives 21.74 A. This is the running current, not a breaker or cable size. What kind of load are you converting, and is it single phase?

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