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Ohm's Law Calculator

Solve voltage, current, resistance and power.

Voltage V
12 V
Current I
2 A
Resistance R
6 ฮฉ
Power P
24 W
Formulas used
V = I ร— R      (Ohm's law)
P = V ร— I      (Joule's law)
derived:  I = V/R ยท R = V/I ยท P = IยฒR = Vยฒ/R

About the Ohm's Law Calculator

Solve the full V, I, R, P quartet from any two knowns. Pick which pair you have โ€” voltage and current, voltage and resistance, current and resistance, or any pair involving power โ€” and the tool derives the remaining two values using Ohm's law and Joule's law, displaying the formulas it applied.

How to use the Ohm's Law Calculator

  1. Select the pair of values you know from the dropdown, for example Power & Voltage.
  2. Enter the two known quantities in the labeled fields.
  3. Read all four results: voltage in V, current in A, resistance in ฮฉ and power in W.
  4. Check the Formulas box to see which relations produced the numbers.

Ohm's Law Calculator FAQ

Which quantities can I start from?

Any two of voltage, current, resistance and power โ€” the dropdown lists all six combinations, including power pairs, and solves the rest.

What formulas are behind the results?

V = I ร— R and P = V ร— I, with the derived forms I = V/R, R = V/I, P = IยฒR and P = Vยฒ/R shown explicitly under the result tiles.

Why do I get an error message?

Negative or zero-denominator inputs cannot produce a physical answer, so the tool asks for valid non-negative numbers instead of returning nonsense.