Ohm's Law Calculator
Solve for voltage, current, or resistance using Ohm's Law.
V
A
Ω
Formula: V = I × R
Worth Knowing
Ohm's Law describes a three-way relationship, so knowing any two of voltage, current, and resistance always gives you the third. A practical use: sizing a current-limiting resistor for an LED. If a 9V supply feeds an LED with a 2V forward voltage drop and you want to cap current at 20 mA, the resistor needs to drop the remaining 7V — solving R = V ÷ I gives 7 ÷ 0.02 = 350Ω. Skipping this step and guessing a resistor value is one of the most common ways beginners burn out an LED on a first electronics project.
How to Use
- Enter Solve for into the first field of the Ohm's Law Calculator.
- Fill in the rest: Voltage, Current, Resistance.
- Your result appears instantly as you type — there's no submit button or page reload.
Formula
V = I × R