Solve any resistive circuit in one step: give the calculator two of voltage, current, resistance, and power, and it derives the other two using V = I × R and P = V × I. Inputs accept SI prefixes the way you actually write them — 4.7k, 20m, 470µ — and results come back formatted the same way, so there is no unit juggling.
Everything runs in your browser. If you are working from a physical part, the resistor color code calculator decodes the bands first; for other conversions the unit converter and math evaluator round out the bench toolkit.
Frequently asked questions
What is Ohm's law?
Ohm's law states that current through a conductor is proportional to the voltage across it: V = I × R. Combined with the power law P = V × I, any two of voltage, current, resistance, and power determine the other two — which is exactly what this calculator solves.
Why do I enter exactly two values?
Two known quantities fully determine a resistive DC circuit. With only one value the system is underdetermined (infinitely many answers); with three you have redundancy that may contradict itself. The calculator therefore takes exactly two and derives the rest.
Can I type values like 4.7k or 20m?
Yes — inputs accept SI prefixes: k (kilo), M (mega), G (giga), m (milli), µ or u (micro), n (nano), p (pico), with or without a unit letter. So 4.7k, 4.7kΩ, and 4700 all mean the same resistance, and results are formatted back with sensible prefixes like 12 mA.
Does this work for AC circuits?
The calculator assumes DC or purely resistive loads. In AC circuits with capacitors or inductors you need impedance and phase angles, not plain resistance — the resistive formulas here are the right starting point but not the whole story.