What is the formula used?

For DC circuits: V = P / I. For AC single-phase circuits: V = P / (I × PF), where PF is the power factor (between 0 and 1). A PF of 1 means a purely resistive load.

What is power factor?

Power factor (PF) is the ratio of real power (watts) to apparent power (volt-amps). It ranges from 0 to 1. Resistive loads like heaters have PF ≈ 1; motors and fluorescent lights typically have PF between 0.7 and 0.95.

Why is current required and not resistance?

When you know both power and current, voltage follows directly from V = P / I without needing resistance. If you know resistance instead, use the Amps to Volts calculator (V = I × R).

Can I use this for three-phase AC?

This tool covers DC and single-phase AC. For three-phase AC the formula is V = P / (√3 × I × PF). A dedicated three-phase calculator is better suited for that use case.

What happens if I enter 0 for current?

Division by zero is undefined, so the tool shows an error. Current must be a positive value greater than zero.

What power factor should I use if I do not know it?

For a conservative estimate use 0.8, which is a common default for mixed loads. For resistive-only loads (heaters, incandescent bulbs) use 1.0.

How much voltage is 100 watts?

It depends on the current. Using V = P / I, 100 W at 10 A is 10 V, while 100 W at about 0.83 A is 120 V. Enter the current (and power factor for AC) to get the exact voltage.

Watts to Volts Calculator

Convert watts to volts for DC circuits (V = P / I) or AC circuits (V = P / (I × PF)) instantly.

Circuit Type

Power (P)

Current (I)

Enter power and current to calculate voltage

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Summary

Calculate voltage from power and current for both DC and single-phase AC circuits. For DC use V = P / I; for AC include the power factor so V = P / (I × PF). Results update as you type — no server needed.

How it works

Choose DC or AC mode using the toggle at the top.
Enter the power in watts (W) in the Power field.
Enter the current in amperes (A) in the Current field.
For AC mode, enter the power factor (0 to 1) — use 1 for purely resistive loads.
The voltage result appears instantly with a full calculation breakdown.
Click "Copy Result" to copy the voltage value to your clipboard.

Use cases

Determine supply voltage needed for a DC motor given its wattage and rated current.
Size a transformer or inverter output voltage for an AC load.
Verify nameplate voltage against measured current and power draw.
Cross-check datasheet specifications before wiring a panel.
Calculate required battery voltage from load power and current rating.
Estimate AC line voltage when only kW and amp readings are available.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu

Watts to Volts Calculator

Use the Watts to Volts Calculator

Summary

How it works

Use cases

Frequently Asked Questions