Ohm's Law Calculator
Solve for voltage, current or resistance using Ohm's Law.
Assumptions used in this calculation
- Constant resistance: Assumes an ohmic (linear) component whose resistance does not change with applied voltage, current or temperature.
- DC circuit: The formula applies to direct current or resistive AC circuits; it does not account for reactance from inductors or capacitors.
About this calculator
Ohm's Law, V = I × R, is the single most-used relationship in electronics, but working it out by hand means first deciding which variable you're solving for, then correctly rearranging the equation, a step that trips up beginners and gets tedious even for experienced technicians checking multiple components. This calculator lets you pick whichever quantity you need (voltage, current, or resistance), enter the other two known values, and instantly returns the result along with the power dissipated (P = V × I), which many manual calculations skip entirely. It's built for the everyday tasks around a circuit: checking whether a resistor is correctly sized for a given supply and load, verifying a power supply won't exceed a component's current rating, or back-calculating an unknown resistance from a measured voltage and current. Because it solves for any of the three variables rather than just one fixed formula, it saves the mental step of rearranging algebra under time pressure.
Worked example
I=2A, R=10Ω
Result: V = 20V, P = 40W
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