Ohm's Law Calculator
Calculate voltage, current, resistance, and power. Enter any two values.
Formula
V = I · R · P = V · I = I²R = V²/R
Tips
- Leave one field blank and fill the other two — the tool solves for the missing quantity.
- Power dissipation determines the resistor wattage rating you need. Choose a rating at least double the calculated power.
- Keep units consistent: milliamps must be converted to amps (divide by 1000) before entry.
Frequently asked questions
Does Ohm’s law apply to all components?
Only to ohmic components, where resistance is constant. Diodes, transistors, and filament lamps are non-ohmic — their resistance changes with voltage or temperature.