Convert between watts (power) and amps (current) using voltage and power factor — supports both watts-to-amps and amps-to-watts, for single-phase or three-phase supply, in W or kW.
How to Use the Watt to Amp Calculator
Choose the conversion direction: Watts/kW to Amps, or Amps to Watts.
Enter the power (or current), the supply voltage, and the power factor.
Select single-phase or three-phase, then click "Calculate".
How Watts, Volts and Amps Relate
In an AC circuit, real power in watts equals voltage × current × power factor, and for a three-phase supply there is an extra factor of √3 (about 1.732). The calculator rearranges the same equation depending on the direction you choose:
Watts to amps: I = P ÷ (V × PF) for single phase, or I = P ÷ (1.732 × V × PF) for three phase.
Amps to watts: P = V × I × PF for single phase, or P = 1.732 × V × I × PF for three phase.
If you choose kW, the value is multiplied by 1,000 before the calculation. Results show current to two decimals, power in whole watts, and power in kW to three decimals.
Worked Examples
Default values: 1,000 W at 230 V with a power factor of 0.9 on single phase gives 1,000 ÷ (230 × 0.9) = 4.83 A.
A 3,000 W geyser is a resistive load, so use a power factor of 1: 3,000 ÷ 230 = 13.04 A. That is why geysers are normally put on a dedicated power circuit rather than a lighting circuit.
Amps to watts: a 16 A single-phase socket circuit at 230 V and power factor 1 can supply 230 × 16 = 3,680 W.
A 10 HP three-phase motor (10 × 746 = 7,460 W output) at 415 V and power factor 0.85 draws about 7,460 ÷ (1.732 × 415 × 0.85) = 12.21 A, before allowing for the motor's efficiency, which makes the actual current a little higher.
Quick Reference: Current for Common Loads
Power
230 V, PF 1
230 V, PF 0.8
415 V three phase, PF 0.8
500 W
2.17 A
2.72 A
0.87 A
1,000 W
4.35 A
5.43 A
1.74 A
1,500 W
6.52 A
8.15 A
2.61 A
2,000 W
8.70 A
10.87 A
3.48 A
3,000 W
13.04 A
16.30 A
5.22 A
5,000 W
21.74 A
27.17 A
8.70 A
10,000 W
43.48 A
54.35 A
17.39 A
Avoiding Common Errors
For three phase, enter the line-to-line voltage, which is 415 V (sometimes quoted as 400 V) on Indian supplies, not the 230 V measured from one phase to neutral. The √3 factor assumes line voltage and a balanced load.
For DC circuits such as a battery or solar panel, set the power factor to 1 and choose single phase; the formula then reduces to I = P ÷ V.
Running current is not starting current. Motors in pumps, compressors and ACs can draw several times their running current for a moment at start-up, which matters when choosing an MCB or inverter.
The current figure tells you the load, not the breaker size. The MCB rating must suit the cable it protects and the type of load, so let a licensed electrician choose it.
Frequently Asked Questions
Single-phase: Current (A) = Power (W) ÷ (Voltage × Power Factor). Three-phase: Current (A) = Power (W) ÷ (√3 × Voltage × Power Factor).
Resistive loads (heaters, incandescent bulbs) are close to 1.0. Motors, fans, and ACs are typically 0.8–0.9. If you're unsure, 0.9 is a common estimate for general household appliances.
At 230 V and a power factor of 1, a 6 A socket corresponds to about 1,380 W and a 16 A socket to about 3,680 W. In practice keep the continuous load comfortably below these figures, and plug heaters, geysers, irons and ACs into 16 A power sockets.
The power is shared across three conductors at a higher line voltage. A 10 kW load at power factor 0.8 draws about 54 A on 230 V single phase but only about 17 A per line on 415 V three phase, which allows thinner cables and smaller breakers.
Multiply horsepower by 746 to get watts, enter that figure, and use the motor's power factor from its nameplate. A 1 HP single-phase pump at 230 V and power factor 0.8 works out to about 4.05 A, plus a little more to cover motor losses.