What is the formula for DC circuits?

For direct current: P = V × I, where P is power in watts, V is voltage in volts, and I is current in amperes.

What is the formula for single-phase AC?

P = V × I × PF, where PF is the power factor (0 to 1). The power factor accounts for the phase difference between voltage and current waveforms in reactive loads.

What is the formula for three-phase AC?

P = √3 × VLL × I × PF, where VLL is the line-to-line voltage. If you enter line-to-neutral voltage (VLN), the tool converts it using VLL = √3 × VLN before applying the formula.

What power factor should I use?

Use 1.0 for purely resistive loads such as incandescent bulbs and heating elements. Use 0.8 as a general default for mixed or unknown loads. Motors and fluorescent lights typically have PF between 0.7 and 0.95.

What is the difference between line-to-line and line-to-neutral voltage?

In a three-phase system, line-to-line voltage (VLL) is measured between any two phase conductors, while line-to-neutral (VLN) is measured from one phase to the neutral. VLL = √3 × VLN, so 208 V line-to-neutral corresponds to 360 V line-to-line.

How do I convert watts to kilowatts?

Divide watts by 1000. The result panel shows both watts (W) and kilowatts (kW) automatically once a result is computed.

Can I convert voltage to watts directly?

No — voltage alone is not enough. Watts measure power, so you also need the current in amps: P = V × I. For AC circuits, multiply by the power factor: P = V × I × PF.

Volts to Watts Calculator

Name: Volts to Watts Calculator
Availability: InStock
Author: Nham Vu

Convert volts and amps to watts for DC, single-phase AC, and three-phase AC circuits using P = V × I formulas.

Circuit Type

P = V × I

Voltage (V)

Current (I)

Enter voltage and current to calculate power

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Summary

Convert volts and amps to watts for DC, single-phase AC, and three-phase AC circuits using P = V × I formulas.

How it works

Select your circuit type: DC, AC Single-Phase, or AC Three-Phase.
Enter the voltage in volts (V).
Enter the current in amperes (A).
For AC modes, enter the power factor (0.01 to 1). Use 1.0 for purely resistive loads.
For three-phase, choose whether your voltage is line-to-line (VLL) or line-to-neutral (VLN).
The watt result and full calculation breakdown appear instantly.
Click "Copy Result" to copy the power value to your clipboard.

Use cases

Estimate the power draw of a DC battery load from its operating voltage and current.
Size a circuit breaker or fuse by knowing the wattage consumed on an AC branch.
Convert motor nameplate data (volts, amps, PF) to kilowatts for energy audits.
Verify that a three-phase panel circuit stays within rated wattage limits.
Calculate generator fuel usage by finding the total wattage of connected loads.
Cross-check appliance wattage labels against measured current and supply voltage.
Convert ampere readings from a clamp meter to watts for billing estimation.
Determine heating element power from supply voltage and rated current.

Frequently Asked Questions

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