kW to Amps Calculator

Enter real power (kW), voltage, power factor, and phase to calculate the current a load draws.

How to Use the kW to Amps Calculator

Real power in kW, voltage, and power factor all feed the result, with a Single-Phase/Three-Phase toggle to match the supply — three numbers and one switch, all live-updating.

This is the reverse of Amps to kW, and it's the more consequential direction of the two in practice: given a known load — a motor nameplate, an appliance spec, a panel's connected kW — figure out the current it will actually draw, which is what determines wire gauge and breaker rating.

Single-phase: I = (kW × 1000) ÷ (V × PF)
Three-phase:  I = (kW × 1000) ÷ (√3 × V × PF)

A 4 kW single-phase load at 230V and a 0.8 power factor draws about 21.7A. Drop the power factor to 1.0 by mistake — treating a motor as if it were a purely resistive heater — and the same 4 kW appears to need only 17.4A, a meaningfully smaller number that understates the real current by 20%.

That gap is where wiring mistakes actually happen. A breaker or conductor sized against the optimistic 17.4A figure will run hot, trip under load, or both, once the real 21.7A shows up on a motor with its actual power factor. Omitting power factor here isn't a rounding error the way it might be elsewhere — it directly changes the current figure that everything downstream (wire gauge, breaker rating, panel capacity) gets sized against, so it's worth pulling the real PF off a nameplate or test report rather than assuming 1.0 out of convenience.

Three-phase changes the number but not the lesson: spreading the same 4 kW across three conductors instead of one brings current down further, but a wrong power factor still throws off every conductor's rating by the same 20% or so, three-phase or not.