What formula does DC use?

DC power is W = A × V. Multiply amperes by volts to get watts directly, since DC has no reactive component.

What is power factor (PF)?

Power factor is the ratio of real power to apparent power, ranging from 0 to 1. Resistive loads (heaters, incandescent bulbs) have PF ≈ 1. Inductive loads (motors, transformers) have lower PF, typically 0.7–0.9.

Why does three-phase use √3?

In a balanced three-phase system the line voltage relates to phase voltage by √3 (≈ 1.732). The formula W = A × V × PF × √3 uses line current and line-to-line voltage, which is the standard nameplate convention.

What is the difference between watts and volt-amps?

Watts (W) measure real power — the work actually done. Volt-amps (VA) measure apparent power. For DC and purely resistive AC, they are equal. For inductive/capacitive AC loads, VA = W / PF, so VA ≥ W.

How do I find the power factor of my appliance?

Check the appliance nameplate or datasheet. It is often listed as "PF", "cos φ", or you can divide rated watts by rated VA. If not listed, use 0.8 as a conservative estimate for motors, or 1.0 for heaters.

Amps to Watts Calculator

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

Enter current (amps), voltage, and power factor to instantly calculate watts for DC or AC single/three-phase circuits.

Input Values

Circuit Type

Current (A)

Voltage (V)

Power Factor (0 – 1)

1.0 = purely resistive; motors typically 0.7–0.9

Enter current and voltage, then press Calculate.

Formula Reference

DC W = A × V

AC 1-Phase W = A × V × PF

AC 3-Phase W = A × V × PF × √3

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Summary

Enter current (amps), voltage, and power factor to instantly calculate watts for DC or AC single/three-phase circuits.

How it works

Select your circuit type: DC, AC single-phase, or AC three-phase.
Enter the current in amperes (A) and the voltage in volts (V).
For AC circuits, enter the power factor (0–1). Resistive loads use PF = 1.
The calculator applies W = A × V (DC), W = A × V × PF (single-phase), or W = A × V × PF × √3 (three-phase).
The result in watts appears instantly and updates as you type.

Use cases

Size a circuit breaker by knowing the wattage a load draws.
Estimate monthly electricity cost from an appliance's amp rating.
Verify that a generator or UPS can handle a given load.
Convert motor nameplate current and voltage to shaft power.
Check three-phase panel capacity for industrial equipment.
Calculate power draw for EV charging stations and battery banks.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu