Are watts always real power?

Yes. By convention, "watts" means real power (W or kW), and "volt-amps" means apparent power (VA or kVA). Some loose nameplates use "watts" when they mean VA - check whether a power factor is also listed to disambiguate.

Should I add the 125% continuous factor here or in the breaker calculator?

This calculator gives raw amps from watts. Apply the 1.25 continuous factor when you size the conductor and breaker (NEC 210.20(A) and 215.3). The breaker size calculator handles that step explicitly.

Does this give RMS or peak amps?

RMS. Voltage and watts are RMS values for AC, so the result is RMS current - which is what every breaker, conductor, and ampacity rating is based on.

Watts to Amps Calculator

Convert watts to amps instantly. Free calculator for single-phase and three-phase circuits with power factor adjustment.

Inputs

Power

Voltage

Power Factor

Phase

Single-PhaseThree-Phase

Result

Current

8.333A

I = P / (V × PF) = 1000 / (120 × 1)

About this calculator

Going from watts to amps requires voltage and (for AC reactive loads) power factor. This is the reverse of the amps-to-watts conversion and shows up whenever you have a load nameplate in watts (a heater, an LED panel) and need to size the wire and breaker.

Formula

Single-phase amps equal watts divided by voltage and power factor. Three-phase divides by √3 times line-to-line voltage times power factor.

Single-phase: I = W ÷ (V × PF)
Three-phase: I = W ÷ (√3 × V × PF)

How to use

Pick single-phase or three-phase.
Enter the wattage and voltage.
Enter power factor (1.0 for resistive, 0.85-0.9 for motors).
Read the result in amps.
Use the result for sizing - then add 25% if the load is continuous (NEC 210.20(A)).

Worked example

Setup

A 1,500 W single-phase 120 V resistive baseboard heater.

Calculation

I = 1500 ÷ (120 × 1.0) = 12.5 A. Continuous load: 12.5 × 1.25 = 15.6 A required.

Answer

The heater draws 12.5 A. For continuous-load sizing, you need a 20 A breaker (next standard size above 15.6 A) and #12 conductors at minimum.

Frequently asked questions

Are watts always real power?: Yes. By convention, "watts" means real power (W or kW), and "volt-amps" means apparent power (VA or kVA). Some loose nameplates use "watts" when they mean VA - check whether a power factor is also listed to disambiguate.
Should I add the 125% continuous factor here or in the breaker calculator?: This calculator gives raw amps from watts. Apply the 1.25 continuous factor when you size the conductor and breaker (NEC 210.20(A) and 215.3). The breaker size calculator handles that step explicitly.
Does this give RMS or peak amps?: RMS. Voltage and watts are RMS values for AC, so the result is RMS current - which is what every breaker, conductor, and ampacity rating is based on.