volts to watts

W = V × I. Volts become watts only through a current: 120 V at 10 A is 1,200 W. Where resistance is known instead of current, W = V² ÷ R yields the same result.

Watts are what you pay for — volts times amps, nothing more. A 120 V bulb drawing 0.5 A burns 60 W, and a 120 V heater pulling 15 A burns 1,800 W. This calculator applies P = V·I, the watt's law companion to Ohm's law, and it is the conversion behind every appliance label, breaker load calculation, and electricity bill in the world.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →
volts
amps
— watts
— —

Source: NIST SP 811 and the 1959 yard-and-pound agreement (0.9144 m, 0.45359237 kg). Every decimal place in the factor above is a defined constant, not a measurement.

volts to watts

Power in watts is the rate of energy use, and P = V·I is exact for DC and for resistive AC loads (which covers heaters, bulbs, and most household appliances; motors and reactive loads carry an additional power factor). The US 120 V / 240 V split means the same 15 A delivers 1,800 W at 120 V but 3,600 W at 240 V — which is exactly why ranges and dryers run on 240 V. Every load calculation that sizes a circuit sums watts first, then converts to amps at the circuit voltage.

watts = volts × amps
P = V·I
Exact watt's law — the product of the voltage and current you provide.

Worked Examples

Example 1: Convert a 120 V bulb drawing 0.5 A

120 × 0.5 = 60 W

Example 2: Convert a 240 V circuit drawing 15 A

240 × 15 = 3,600 W

Example 3: Convert a 12 V load drawing 10 A

12 × 10 = 120 W

Common volts to watts Values

voltsampswattsContext
120 V0.5 A60 WIncandescent bulb.
120 V5 A600 WMicrowave oven.
120 V15 A1,800 WSpace heater at full load.
240 V15 A3,600 WElectric dryer.
12 V10 A120 WAutomotive accessory.

Engineering Context

Volts-to-watts is the bridge between the electric hub and the energy family — watts are the electric unit that connects to watts to kW and kWh billing via Wh to kWh. The reverse conversion lives on watts to volts, and the current side on watts to amps.

A voltage on its own says nothing about power, and this page is where that becomes obvious. A static charge of several thousand volts carries microamperes and converts to a few milliwatts, while a twelve volt battery delivering one hundred amperes converts to more than a kilowatt. The product is what matters, which is why appliances carry wattage ratings rather than voltage ratings, and why a current-limited supply at high voltage is not the danger its number suggests while a low-voltage high-current source very much is. In alternating-current work the same product needs the power factor applied, so the result here is the apparent power in volt-amperes unless the load is resistive.

More: W to V · W to A · W to kW · Electric Guide · Electric Hub

Related Unit Converters

watts to volts watts to amps Watts to Kilowatts Electric Conversion Guide Electric Converters

Frequently Asked Questions

How do I convert volts to watts?

Multiply volts by amps: P = V·I. A 120 V device drawing 0.5 A consumes 60 W. If you know resistance instead, P = V²/R gives the same answer.

Why do dryers and ranges use 240 volts?

Because power scales with voltage: P = V·I. The same 15 A breaker delivers 1,800 W at 120 V but 3,600 W at 240 V — double the heating capacity from the same wire size and breaker.

Is volts times amps always watts?

For DC and resistive AC loads (heaters, bulbs), yes — exactly. For motors and other reactive loads, the real power is V·I·power factor, and the power factor (usually 0.7–0.95) must be included.