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Watts to Volts Calculator

Convert watts to volts using either the current (V = W ÷ A) or the resistance (V = √(W × R)), for DC, single-phase, and three-phase. WattSimple also names the nearest standard US system voltage, so you can tell straight away whether the answer describes a real circuit.

Watts alone do not set a voltage: a 1,500 W load is 1,500 W whether it runs on 120 V or 240 V. You need the current or the resistance to pin the voltage down. In practice you rarely calculate a supply voltage; you read it off the system and use it to find the current instead.

Voltage

120 V

Power
1,500 W
Current
12.5 A
In kilowatts
1.5 kW

Nearest standard system voltage

120 V: standard receptacle / lighting; your result is +0% from 120 V.

A result far from every nominal voltage usually means the current or resistance figure is off. Utilization equipment is built to tolerate roughly ±5% of nominal (ANSI C84.1 Range A).

Measure the real amps and volts

The converter works from nameplate or assumed figures. A clamp meter reads the actual current on one conductor without breaking the circuit; clamped around a whole cord it reads close to zero. A multimeter reads the voltage at the receptacle or terminals. Opening a panel or a live box is work for someone qualified.

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Frequently asked questions

Divide watts by amps: V = W ÷ A. On AC, divide by the power factor too, and for three-phase divide by 1.732 × amps × power factor. If you know resistance instead of current, V = √(W × R). Example: 1,500 W drawing 12.5 A works out to 120 V.

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Sources & standards

This tool's methodology and data follow US standards and authoritative public datasets: