Physics

Ohm's Law Calculator

Calculate voltage, current, resistance, and power using Ohm's Law (V=IR, P=VI)

Last updated: How we build & verify

How it works

Relates voltage, current, and resistance in an electrical circuit. Given any two of the three, the calculator finds the third and also computes power dissipated.

Formula
V = I × R   |   P = V × I = I² × R = V² / R
Variables
  • Vvoltage (volts)
  • Icurrent (amperes)
  • Rresistance (ohms)
  • Ppower (watts)
Notes
  • Ohm's law applies to linear resistors. Semiconductors, LEDs, and inductive loads do not follow it exactly.

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Frequently Asked Questions

Ohms Law runs right in the browser tab you already have open. No install, no account, no cost.

Ohms Law follows the standard method used in textbooks and technical references for this calculation, and we show the formula or approach on the page itself so you can check the working rather than trust a black box. Found an edge case that breaks it? Use the feedback button in the bottom-right corner.

Ohm's Law Calculator | ExaCalc