How Ohm's Law works
Ohm's Law links the three basics of an electric circuit: voltage (V), current (I) and resistance (R). Know any two and you can find the third. This calculator also works out power (P). Leave one field blank and fill the other two.
The Ohm's Law formula
V = I x R. Rearranged: I = V / R, and R = V / I. Power is P = V x I, which also equals I squared times R.
Worked example
A 12 volt supply pushing 2 amps means the resistance is 12 / 2 = 6 ohms, and the power is 12 x 2 = 24 watts.
Frequently asked questions
What is Ohm's Law?
It states that voltage equals current times resistance (V = IR). It is the fundamental relationship for any simple electrical circuit.
How do I find power?
Power equals voltage times current (P = VI). It also equals current squared times resistance, or voltage squared divided by resistance.
Which two values do I enter?
Any two of voltage, current and resistance. Leave the one you want to find blank, and the calculator fills it in along with power.