Amps to Watts Calculator
Convert amps to watts: enter current, voltage, and power factor to get power in watts and kilowatts, using the standard P = A × V × PF formula.
How this calculator works
Circuits and breakers are rated in amps, but appliances and utility bills are measured in watts. This calculator turns a current draw into the power it represents so you can compare devices, size backup power, or read a load in the same units as its rating.
Enter the current, the circuit voltage, and the power factor, and the tool returns power in both watts and kilowatts.
Formula: Watts = Amps × Volts × Power Factor.
Worked example
A 15 A load on a 120 V circuit with a power factor of 1:
- Volts: 120 V
- Power factor: 1
- Power = 15 × 120 × 1 = 1800 W (1.8 kW)
At 120V, power factor 1
| Amps | Watts |
|---|---|
| 5 A | 600 W |
| 10 A | 1200 W |
| 15 A | 1800 W |
| 20 A | 2400 W |
How to use
Enter the current in amps, your circuit voltage (commonly 120 V or 240 V), and the power factor for the load. Use a power factor of 1 for heaters and lamps, or the nameplate value for motors and electronics. The result gives you both watts and kilowatts so you can match the load to appliance ratings or generator capacity.
Electrical work is code-governed and safety-critical. Confirm circuit, breaker, and conductor sizing with a licensed electrician and your local code.
Frequently asked questions
How do I convert amps to watts?
Multiply the current by the voltage and the power factor. For 15 A on a 120 V circuit with a power factor of 1, the power is 15 × 120 × 1 = 1800 W, or 1.8 kW. Make sure the voltage matches the actual circuit, since the same amps at 240 V would produce twice the wattage.
What is the difference between watts and kilowatts?
A kilowatt is simply 1000 watts, so you divide watts by 1000 to get kilowatts. In the worked example, 1800 W is the same as 1.8 kW. Watts are handy for individual devices, while kilowatts show up on utility bills and on the ratings for larger appliances and whole circuits.
Why does 15 A at 120 V give 1800 watts?
Power equals current times voltage times power factor, so 15 × 120 × 1 comes to 1800 W, which is 1.8 kW. With a resistive load the power factor is 1, so the amps and volts multiply straight through. On a higher-voltage circuit the same 15 A would deliver more watts, because voltage is a multiplier in the formula.
Does power factor change the result?
Yes. Power factor is a multiplier, so a load with a power factor below 1 produces fewer real watts than amps and volts alone would suggest. Resistive loads such as heaters and lamps run at a power factor of 1, giving the full amps-times-volts figure. Motors and electronics often run lower, so use their nameplate power factor for an accurate wattage.
Estimates only. Verify quantities with your supplier before purchasing.