Watts to Amps Calculator
Convert watts to amps for any circuit: enter power, voltage, and power factor to get the current draw, using the standard I = W ÷ (V × PF) formula.
How this calculator works
Watts measure how much power a device uses, but breakers and wire are sized by amps — the current flowing through the circuit. This calculator converts one to the other so you can check whether a load fits the circuit it is on.
Enter the wattage, the circuit voltage, and the power factor, and the tool returns the current draw in amps.
Formula: Amps = Watts ÷ (Volts × Power Factor). Power factor is 1 for resistive loads (heaters, incandescent bulbs) and lower for motors.
Worked example
A 1500 W device on a 120 V circuit with a power factor of 1:
- Volts: 120 V
- Power factor: 1
- Current = 1500 ÷ (120 × 1) = 12.5 A
At 120V, power factor 1
| Watts | Amps |
|---|---|
| 600 W | 5.0 A |
| 1200 W | 10.0 A |
| 1800 W | 15.0 A |
| 2400 W | 20.0 A |
How to use
Enter the device wattage, 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. Compare the resulting amps against the circuit’s breaker rating to confirm the load fits safely.
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 watts to amps?
Divide the wattage by the voltage times the power factor. For a 1500 W device on a 120 V circuit with a power factor of 1, the current is 1500 ÷ (120 × 1) = 12.5 A. Keep the voltage and power factor consistent with your actual circuit, since a lower voltage or lower power factor both raise the amps for the same wattage.
What power factor should I use?
Power factor is 1 for resistive loads such as heaters and incandescent bulbs, so watts divided by volts gives the amps directly. Motors, transformers, and many electronics run at a lower power factor, which means they draw more current than a simple watts-over-volts figure suggests. If you do not know the power factor, use the value printed on the device nameplate.
Why does a 1500 W device draw 12.5 A at 120 V?
At 120 V with a power factor of 1, current equals 1500 ÷ (120 × 1), which works out to 12.5 A. Voltage and power factor sit in the denominator, so a higher voltage would lower the amps and a lower power factor would raise them. The 12.5 A result assumes a purely resistive load on a standard 120 V circuit.
Does higher voltage mean fewer amps for the same watts?
Yes. Voltage is in the denominator of the formula, so the same wattage on a higher-voltage circuit draws fewer amps. A device pulling 12.5 A at 120 V would draw roughly half the current on a 240 V circuit at the same wattage and power factor. That is why large appliances are often wired for 240 V, to keep the current and conductor size down.
Estimates only. Verify quantities with your supplier before purchasing.