What this converter does
This converter turns current into real power in watts, for single-phase and three-phase circuits. Enter the voltage and power factor, pick the phase, and read the watts — or swap the arrow to size the current for a known load. Leave PF at 1 for a purely resistive load.
For AC, real power is voltage times current times power factor; three-phase adds a √3 factor. For a resistive load such as a heater, power factor is 1. For power in kilowatts, see the kW to Amps converter.
The units it covers
Watts from current depend on the phase, the voltage and — for AC — the power factor.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| Current | A | I | Amperes the circuit carries |
| Real power | W | P | Useful power delivered |
| Voltage | V | V | Line-to-line for three-phase |
| Power factor | PF | cos φ | 1 for resistive; under 1 for motors |
The formula
Real power is voltage times current times power factor:
W = V × A × PF (× √3 for three-phase)Where:
- A = the current you typed
- V = supply voltage (line-to-line for 3-phase)
- PF = power factor, 1 for resistive loads
Worked example
A single-phase 230 V circuit carries 10 A at a power factor of 1. Find the power.
W = V × A × PF230 × 10 × 1 = 2,300 WThe load draws 2,300 W — that is 2.3 kW at unity power factor.
The units in this example
The amperes flowing in the circuit. With voltage and power factor it gives real power; the three-phase form multiplies by √3.
- W = V × A × PF — 1ph
- W = √3 × V × A × PF — 3ph
- 1 A at 230 V, PF 1 = 230 W
- 1 A at 400 V, 3ph, PF 1 = 693 W
The useful power delivered to the load, in watts. One thousand watts is a kilowatt; it equals voltage × current × power factor.
- 1 kW = 1,000 W
- A = W ÷ (V × PF) — 1ph
- 1 W = 1 J per second
- resistive load: PF = 1
FAQ
Sources
US DOE — estimating energy use · US EIA — electricity basics