Ohm's Law Calculator
Fill in any two of the four fields — the other two are calculated automatically.
Enter exactly two values — clear a field if three or more are filled.
Free Ohm's law calculator (the "power wheel") — fill in any two of voltage, current, resistance, and power, and the other two are calculated automatically.
How it works
- Fill in any two of the four fields: voltage, current, resistance, power
- The other two are calculated instantly
- Clear a field and fill in a different one to solve a different combination
Frequently asked questions
Why four fields instead of picking what to solve for?
Ohm's law (V=IR) plus the power equation (P=VI) together mean any two known values determine the other two — rather than making you pick from six possible combinations in a dropdown, this just watches which two fields you've filled in.
What if I fill in three fields?
It shows a message asking you to leave exactly two filled — with three values you might be describing an inconsistent circuit, so it doesn't guess which one to trust.
Related tools
From the blog
Update history
- 2026-09-02 Launched: Ohm's law / power wheel calculator — fill any two of V/I/R/P and the rest are solved automatically. Entirely client-side.