← Back to all tools

Ohm's Law & Power

⚡ Electrical-Electronics · Voltage, current, resistance, and power from any two known quantities

🔒

A free EngineersLab account is required to use this tool.

V=IRP=VIV = IR \qquad P = VI

Ohm’s law is the cornerstone of electric circuit analysis: the voltage drop across a resistor is directly proportional to the current flowing through it. This simple relationship (V = I·R), together with the power formula (P = V·I), allows the other two of the four fundamental electrical quantities (voltage, current, resistance, power) to be calculated whenever any two are known.

This tool supports three different known-pair scenarios: Voltage+Current, Voltage+Resistance, Current+Resistance. Whichever two are known, all remaining quantities are calculated automatically.

Practical note: Ohm’s law is only valid for ohmic (linear) elements — for non-linear elements like diodes and transistors, this simple relationship doesn’t hold and their more complex current-voltage characteristics must be consulted.

✅ Verified

This tool's calculation logic has been checked against a hand-computed numerical verification test. Test source: src/lib/calc/ohm.test.ts.

  • [5] Alexander, Charles K. and Sadiku, Matthew N. O.. Fundamentals of Electric Circuits, 7 ed.. McGraw-Hill, 2021.

Results are for educational and preliminary-sizing purposes; final engineering design decisions must reference the relevant standards and a licensed engineer's approval.