How do I convert amps to watts?

For DC circuits multiply current by voltage: P = V times I. For single-phase AC circuits also multiply by the power factor: P = V times I times PF. A 10 A load on a 240 V AC circuit with PF = 1.0 uses 2,400 W.

What is the difference between watts and volt-amps?

Watts (W) measure real power, which is the energy actually converted to heat, light, or mechanical work. Volt-amps (VA) measure apparent power, which is the total current draw on the circuit. They are equal only when the power factor is 1.0. For inductive or capacitive loads the VA rating is higher than the watt rating.

How many watts is 10 amps at 240 volts?

At unity power factor (PF = 1.0), 10 A on a 240 V supply equals 10 times 240 = 2,400 W or 2.40 kW. If the power factor is 0.9, the real power is 10 times 240 times 0.9 = 2,160 W.

Amps to Watts Calculator

This calculator converts current in amperes to power in watts for both DC and single-phase AC circuits. Knowing how many watts a device uses is essential for comparing running costs, planning generator capacity, designing battery systems, and checking whether a circuit is overloaded. For a DC circuit the formula is P = V times I, where P is power in watts, V is voltage in volts, and I is current in amperes. For a single-phase AC circuit you multiply by the power factor as well: P = V times I times PF. The power factor is a number between 0 and 1 that reflects how efficiently the load uses the current drawn. A kettle, toaster, or electric heater is purely resistive with PF = 1.0, so all the current goes directly into useful heat. A motor or fluorescent light has a lower power factor, typically 0.8 to 0.95, meaning it draws more current than its watt rating alone would imply. You enter the current in amps, supply voltage, and power factor, and the calculator returns the real power in watts and kilowatts along with the apparent power in volt-amps. Select DC mode to calculate without a power factor. For the default values of 10 A, 240 V, and PF 1.0, the power is 2,400.00 W or 2.40 kW. This tool covers single-phase calculations only; three-phase power uses a different formula involving the square root of three.

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Circuit type

Current (I)

Voltage (V)

Power factor (PF)

2400.00 W

real power

Kilowatts2.40 kW

Apparent power2400.00 VA

How it works

For DC: P = V times I. For single-phase AC: P = V times I times PF. Apparent power (VA) is always V times I regardless of power factor. Real power equals apparent power times PF. Kilowatts are watts divided by 1,000. Power factor is clamped between 0.01 and 1.0 to prevent nonsensical results. In DC mode the power factor is fixed at 1.0.

Worked example

A circuit draws 10 A at 240 V with a power factor of 1.0. Real power = 240 times 10 times 1.0 = 2,400.00 W = 2.40 kW. Apparent power = 240 times 10 = 2,400.00 VA. These match the default values pre-filled above.

Related calculators

Watts to Amps Calculator: the reverse conversion from power and voltage to current.
Electrical Power Calculator: find power using P=VI, P=I²R, or P=V²/R.
Ohm's Law Calculator: solve for voltage, current, or resistance using V=IR.
Percent Error Calculator: compare measured power readings against expected values.

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