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Ohms Law Calculator

Ohm's law links voltage, current and resistance. Enter any two values and the calculator finds the others, including electrical power.

How it works Report a problem

Ohm's Law Calculator

V = I × R — find voltage, current, resistance, or power

V = I × R  |  P = V × I = I²R = V²/R
V
A
Ω
Voltage
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Voltage (V)
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Current (I)
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Resistance (R)
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Power (P)
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Step-by-Step
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Ohm's law is the first and most-used equation in electronics: voltage, current and resistance bound together so that any two fix the third. This calculator solves the triangle in every direction and adds the power the component will dissipate.

How to use this calculator

  • Enter any two of: voltage, current, resistance.
  • Press calculate to see the third value, and the power.

Power is the part that burns things

The law's quiet fourth quantity, power (P = V × I), decides whether a resistor survives. A resistance calculation can be perfectly right while the chosen component still overheats and fails, because its wattage rating was never checked. This calculator shows power alongside the trio for exactly that reason.

Frequently asked questions

What is Ohm's law formula?
V = I × R. Rearranged: I = V/R and R = V/I. It holds for ohmic materials at constant temperature.
What are the units in Ohm's law?
Volts (V), amps (A) and ohms (Ω). One ohm lets one amp flow under one volt.
Does Ohm's law apply to everything?
No. Filament bulbs, diodes and many electronics are non-ohmic: their resistance changes with temperature or voltage. The law applies cleanly to resistors and metals under steady conditions.