Calculator

Amps to Watts Calculator

Enter running current and circuit voltage to estimate real power in watts. For AC, adjust the power factor if you know it.

Not sure what to enter? Read the step-by-step guide.

Your inputs

Circuit type

Voltage V

Use the voltage of the circuit you're measuring.

Running current A

This conversion uses running values, not startup surge.

AC power factor

What does power factor mean?

For AC, power factor (PF) relates real watts to volts × amps. Use the device specification or a suitable measurement. PF = 1 is an assumption, not a value to use for every device.

The default power factor of 1 is an assumption. Use your device's actual value if available.

The prefilled numbers are examples, not recommended values for your equipment. Results update as you type. Your inputs stay in this browser.

Amps to watts conversion

How much power your device uses

Estimated real power

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This is a running-load estimate, not a wire, fuse, breaker, inverter, or generator sizing recommendation.

Edit your inputs

See calculation details, assumptions and sources

For DC: watts = volts × amps. For single-phase AC: real watts = RMS volts × amps × power factor.

At 120 V AC and power factor 1, 12.5 A × 120 V = 1,500 W. At power factor 0.8, the same voltage and current correspond to 1,200 W.

The AC default of 1 is an assumption, not a measured power factor. If the actual factor is lower, the watts-to-amps result will understate running current; the amps-to-watts result will overstate real power. AC voltage and current here are RMS values. This tool covers DC and single-phase AC only.

It does not account for startup surge, inverter loss, changing voltage, or installation requirements. Use the equipment's actual specifications when available. See the site methodology and the U.S. Department of Energy's electrical science handbook for power-factor background.

Need the reverse conversion? Use the Watts to Amps Calculator.