What formula is used for DC circuits?

For DC circuits: I(A) = P(W) / V(V). Current equals power divided by voltage.

What formula is used for single-phase AC circuits?

For single-phase AC: I(A) = P(W) / (V(V) × PF). The power factor (PF) accounts for the phase difference between voltage and current in AC systems.

What formula is used for three-phase AC circuits?

For three-phase AC: I(A) = P(W) / (√3 × V(V) × PF). The √3 factor (approximately 1.7321) accounts for the three-phase relationship. Voltage is the line-to-line voltage.

What is the power factor?

The power factor (PF) is a value between 0 and 1 that represents how efficiently AC power is being used. Purely resistive loads such as heaters have PF = 1. Inductive loads such as motors typically have PF between 0.7 and 0.95.

Why does DC not use a power factor?

DC circuits have no frequency, so there is no phase difference between voltage and current. Power factor only applies to AC circuits where reactive components cause voltage and current to be out of phase.

What is the difference between watts and volt-amps?

Watts (W) measure real power — the actual work performed. Volt-amps (VA) measure apparent power. They are related by: W = VA × PF. For DC and purely resistive AC loads, watts equal volt-amps.

Watts to Amps Calculator

Convert watts (W) to amps (A) for DC, single-phase AC, or three-phase AC circuits instantly.

Circuit Parameters

Circuit Type

Power (W)

Voltage (V)

Result

Enter values and press Calculate

Formula Reference

DC Circuits

A = W / V

Single-Phase AC

A = W / (V × PF)

Three-Phase AC

A = W / (√3 × V × PF)

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Summary

This calculator converts electrical power measured in watts (W) to current measured in amperes (A). It supports three circuit types: DC circuits, single-phase AC circuits, and three-phase AC circuits, each using the correct electrical formula. Enter the power in watts, the voltage in volts, and (for AC circuits) the power factor to get the current in amps.

How it works

Select your circuit type: DC, single-phase AC, or three-phase AC.
Enter the power in watts (W).
Enter the voltage in volts (V).
For AC circuits, enter the power factor (between 0 and 1).
The calculator applies the correct formula and displays the result in amperes (A).
Use the Reset button to clear all fields.

Use cases

Determine the current draw of an appliance from its wattage rating.
Size circuit breakers and wiring for known power loads.
Calculate fuse ratings for residential and commercial equipment.
Convert generator or UPS rated watts to output current.
Check if an outlet can supply enough current for a high-wattage device.
Size cables and conductors based on equipment power consumption.
Verify motor nameplate current from rated horsepower and voltage.
Design solar panel systems by converting panel wattage to current output.

Frequently Asked Questions

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