Watt and Ampere Calculator
Reference Guide

Electrical Formulas — Watts, Amps, Volts, Ohms

A complete reference for the most common electrical calculation formulas. Covers Ohm's Law, Watt's Law, AC power factor, and three-phase relationships. Use the calculator above for instant results.

Conversion direction
Electrical system
Quick voltage presets
Calculated result1000 W · 120 V · DC
8.333 A
Formula usedI = P / V

Custom voltage is always supported.

Formulas Used

DCI = P / V

No power factor needed for DC circuits.

AC 1φI = P / (V × PF)

Single-phase AC — multiply voltage by power factor.

AC 3φI = P / (√3 × V × PF)

Three-phase AC — divide by √3 ≈ 1.732.

Frequently Asked Questions

What is Ohm's Law?

Ohm's Law: V = I x R. Voltage (V) equals current (I) multiplied by resistance (R). Rearranged: I = V/R and R = V/I.

What is Watt's Law?

Watt's Law: P = V x I. Power in watts equals voltage times current. Combined with Ohm's Law: P = I² x R and P = V²/R.