Ohm's Law Converter

Solve any two unknowns among voltage, current, resistance, and power from any other two.

Solve voltage, current, resistance and power instantly. Free Ohm’s law calculator from any two known electrical values.

About Ohm's Law

Solve any two unknowns among voltage, current, resistance, and power from any other two.

Fill any two fields; the twelve rearrangements of V=IR and P=VI cover every pair. Leave the unknowns blank — zeros or guesses distort the solution, so exactly-two-known is enforced.

Results assume ideal DC resistive circuits. AC, reactive loads, and temperature drift need deeper analysis. Everything runs in your browser.

Where it is used

Sizing resistors and fuses, checking LED circuits, verifying power supplies, and electronics homework.

How to use the Ohm's Law

  1. Voltage V (leave blank if unknown) — enter the value (e.g. 12).
  2. Current A (leave blank if unknown) — enter the value (e.g. 2).
  3. Resistance Ω (leave blank if unknown) — enter the value.
  4. Power W (leave blank if unknown) — enter the value.
  5. Calculate — press the Calculate button to see the result instantly above.

Formula

All 12 forms of V=IR and P=VI — any two known values solve the other two.

Examples

Example

voltage:12
current:2
resistance:
power:
Result: R = 6 Ω, P = 24 W

Frequently Asked Questions

Why must exactly two fields be filled?
Two independent equations (V=IR, P=VI) determine two unknowns. One known leaves infinite solutions; three over-constrains and may contradict.
Does this work for AC circuits?
Only for purely resistive DC-equivalent cases. AC needs impedance (complex numbers) and phase — use an AC power calculator.
Why NaN or no solution sometimes?
Dividing by a zero known value (e.g. finding current with 0 Ω implies infinite current). Real circuits would fault first.
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