Volts to Watts: Conversion Formula, Calculator & Chart

Need to convert volts to watts? Voltage alone isn't enough to calculate electrical power—you also need to know the current and, for some AC circuits, the power factor. In this guide, you'll learn how to convert volts to watts for DC, single-phase AC, and three-phase AC systems, with formulas and practical examples to help you calculate power accurately.

Volts to Watts Calculator

Enter the voltage in volts (V) and current in amps (A) to calculate power in watts (W). For AC circuits, you can also enter the power factor (PF) to calculate real power.

For a basic DC circuit, use Watts = Volts × Amps. For single-phase AC, multiply voltage by current and the power factor. Voltage alone is not enough to determine wattage because the result depends on the current flowing through the circuit.

How to Convert Volts to Watts

To convert volts to watts, you need to know more than the voltage alone. Electrical power depends on the voltage and the amount of current flowing through the circuit. The calculation also varies depending on whether the circuit uses DC or AC power.

For a DC circuit, multiply voltage by current. For AC circuits, the power factor may need to be considered, while three-phase systems use a different calculation.

Volts to Watts Formula for DC Circuits

For a basic DC circuit, electrical power is calculated by multiplying voltage by current:

P = V × I

Here, P is power in watts (W), V is voltage in volts (V), and I is current in amps (A).

For example, a 120V device drawing 5A uses:

120V × 5A = 600W

The same voltage can produce different wattages depending on the current. A 120V device drawing 2A uses 240W, while one drawing 10A uses 1,200W. This is why there is no fixed wattage for a given voltage without knowing the current.

Single-Phase AC Volts to Watts Formula

For single-phase AC power, multiplying voltage by current gives apparent power, but it does not always represent the actual power consumed by the device. The difference is related to the power factor (PF), which describes how effectively the electrical current is converted into useful power.

To calculate real power:

P = V × I × PF

For example, a 120V appliance drawing 5A with a power factor of 0.8 consumes:

120V × 5A × 0.8 = 480W

If the load is primarily resistive, such as an electric heating element, the power factor is typically close to 1. In that case, voltage multiplied by current provides a close approximation of real power.

Three-Phase AC Volts to Watts Formula

Three-phase AC systems distribute power across three electrical phases, so their power calculation differs from a single-phase circuit. For a balanced three-phase system using line-to-line voltage, the formula is:

P = √3 × V × I × PF

For example, a 480V three-phase system drawing 10A with a power factor of 0.8 has a real power of approximately:

√3 × 480V × 10A × 0.8 ≈ 6,651W

That is about 6.65kW of real power.

When using a three-phase rating, check whether the stated voltage is line-to-line or line-to-neutral before applying the formula. Using the wrong voltage reference can produce an incorrect wattage calculation. Three-phase power is commonly used in commercial, industrial, and other higher-power electrical systems.

Volts to Watts Using Resistance

If the current is not known but the voltage and resistance are available, you can calculate power using Ohm's law:

P = V² ÷ R

Here, R is resistance measured in ohms (Ω).

For example, a circuit operating at 120V with a resistance of 24Ω has a power of:

120² ÷ 24 = 600W

This provides another way to calculate wattage when resistance is known instead of current. It is particularly useful for simple resistive loads where voltage and resistance are available.

Volts to Watts Conversion Table

The wattage for a given voltage depends on the current. The table below shows common volts to watts conversions at different current ratings, calculated using Watts = Volts × Amps.

For example, 120 volts to watts varies with the current: 120V at 1A is 120W, while 120V at 5A is 600W. The same calculation applies to other common voltages, including 5 volts to watts, 115V, and 240 volts to watts.

Voltage	1A	2A	3A	4A	5A
5V	5W	10W	15W	20W	25W
12V	12W	24W	36W	48W	60W
24V	24W	48W	72W	96W	120W
48V	48W	96W	144W	192W	240W
115V	115W	230W	345W	460W	575W
120V	120W	240W	360W	480W	600W
240V	240W	480W	720W	960W	1,200W

Volts to Watts Example: 120V Blender

Suppose you have a 120V blender that draws 11.5 amps while operating. To calculate its power requirement:

Watts = Volts × Amps

120V × 11.5A = 1,380W

The blender therefore requires approximately 1,380W while operating at this load. Because the actual power requirement depends on the current draw, the wattage cannot be determined from the 120V rating alone.

Using Volts and Watts to Size a Power Station

When choosing a portable power station, the appliance's wattage indicates how much power the inverter needs to deliver. Since the blender requires about 1,380W while running, choose a power station with a continuous AC output higher than 1,380W.

You should also check the appliance's startup or surge power. Devices with motors, compressors, or pumps may briefly require more power when starting than they use during normal operation. The power station's surge output should be high enough to handle this temporary demand.

In addition to output power, consider the power station's battery capacity, measured in watt-hours (Wh). Watts determine whether the power station can run the appliance, while watt-hours help determine how long it can run.

Conclusion

To convert volts to watts, you need to know the current as well. For a basic DC circuit, multiply volts by amps using P = V × I. For AC power, the calculation may also require the power factor, with different formulas for single-phase and three-phase systems.

The key point is that voltage alone does not determine wattage. The same voltage can correspond to different power levels depending on the current. Use the appropriate volts to watts formula for the type of circuit and the available electrical information to calculate the actual power requirement.