Enter any two of voltage, current and resistance and this calculator finds the rest, plus power.
Understanding the ohm's law calculation
Ohm’s law links voltage, current and resistance. Enter any two of the three and this calculator solves for the third and also gives the power.
It’s a basic tool for electronics, wiring and physics problems.
How to fill it in
- Enter any two of voltage (V), current (I) and resistance (R).
- Leave the unknown blank.
- Read the solved value and the power.
The calculation
V = I × R · I = V ÷ R · R = V ÷ I
power P = V × I
Frequently asked questions
What is Ohm’s law?
It states that voltage equals current times resistance (V = IR). Rearranged, it also gives current and resistance.
How do I find power?
Multiply voltage by current (P = V × I). The calculator shows power whenever it can work out both.
What units does it use?
Volts, amps and ohms, giving power in watts. Keep your inputs in these base units for correct results.