Voltage isn't always labeled on a circuit — but if you know the power and current, the Watts to Volts Calculator can work it out for you. Enter your power (in W, mW, or kW), select your current type (DC, AC single-phase, AC three-phase, or impedance-based), then provide the current and any relevant power factor or system impedance to get the voltage in volts, the formula applied, and your power converted to watts.
Voltage
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Formula Used
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Power in Watts
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For DC circuits: V = P / I (voltage equals power divided by current). For AC single-phase: V = P / (PF × I) where PF is power factor. For AC three-phase: V = P / (√3 × PF × I).
A watt (W) is the unit of power in the International System of Units. It measures the rate of energy transfer and is equivalent to one joule per second. In electrical terms, one watt equals one volt times one ampere.
A volt (V) is the unit of electrical potential difference or voltage. It represents the potential difference that drives one ampere of current through a resistance of one ohm, consuming one watt of power.
No, power factor is only required for AC circuits. DC circuits use the simple formula V = P / I. Power factor accounts for the phase difference between voltage and current in AC systems.
System impedance (measured in ohms) is the total opposition to current flow in a circuit. Use impedance when you know the power and impedance but not the current, using the formula V = √(P × Z).
Yes, the calculator supports milliwatts (mW), watts (W), and kilowatts (kW). Simply select the appropriate power unit and the calculation will be adjusted automatically.
Single-phase AC uses V = P / (PF × I), while three-phase AC uses V = P / (√3 × PF × I). Three-phase systems include the factor √3 (approximately 1.732) because power is distributed across three phases.