Electrical & Electronics

Watts to Amps & AC Power Calculator

Convert watts, amps and VA for single-phase or balanced three-phase AC with power factor.

Your inputs

Your results

Current: —

Active power · P: —

Apparent power · S: —

Reactive power magnitude · Q: —

FormulaP = V × I × PF

Assumes sinusoidal AC and balanced three-phase loads. Motor starting current is not included. Reactive power is shown as a magnitude.

Convert AC watts, apparent power and current

Calculate current, active power, apparent power and reactive power from one known quantity, voltage and power factor. The tool supports single-phase AC and a balanced three-phase model. Its reactive-power relationship represents the sinusoidal power triangle; the calculation does not model waveform distortion, phase imbalance or transient behavior.

Step by step

Choose single-phase or three-phase operation. Enter the RMS supply voltage: across the load for single-phase operation, or line-to-line voltage for the balanced three-phase model.
Choose the quantity you know: active power in W, apparent power in VA or current in A. Enter its value and unit, then set the power factor from the load's specifications or measurements.
Review all four results and the formula. Check the phase choice, voltage definition and units before comparing another load or printing the calculation.

Settings and limits

Phase and voltage: For single-phase operation, S = V × I. For balanced three-phase operation, S = √3 × V × I, using line-to-line voltage and line current. Enter total three-phase power when power is the known quantity.
Power factor: Power factor must be greater than 0 and no greater than 1. Active power is P = S × PF, so a lower PF requires more current for the same active power and voltage. Reactive-power magnitude is Q = S × √(1 − PF²); its sign is not determined.
Units and known quantity: W and kW represent active power; VA and kVA represent apparent power. They are equal in magnitude only when PF = 1. Recognized unit suffixes override the unit selector. Changing the known quantity uses the previous valid result as the new starting value.

Worked example

Select single-phase operation and active power as the known quantity. Enter 230 V, 1840 W and PF = 0.8. Compare the results with the table below.

Expected result
V	PF	P	I	S	Q
230 V	0.8	1840 W	10 A	2300 VA	1380 var

I = 1840 / (230 × 0.8) = 10 A. Apparent power is 2300 VA and reactive-power magnitude is 1380 var. Dividing watts by voltage alone would give 8 A and omit the power-factor adjustment.

Questions and troubleshooting

Can I use this result to select a cable or protective device?

This tool calculates an idealized current and power relationship. It does not check installation conditions, conductor capacity, protective-device behavior or equipment starting current. Those decisions need the relevant equipment and installation requirements.

Does it distinguish inductive and capacitive reactive power?

The output is a nonnegative reactive-power magnitude. The inputs contain no leading or lagging selection, so the calculator does not assign an inductive or capacitive sign or design power-factor correction.

Why are the results blank?

Check that voltage is positive, the known value is nonnegative and power factor is within its allowed range. Ensure the unit matches the chosen known quantity, then correct the highlighted field or reset.