Electronics Tools
Ohm’s Law Calculator
Solve voltage, current, resistance, and power for basic DC circuits. Pick the unknown value, enter the other two values, and the calculator handles the unit conversion.
What this tool doesSolves the missing Ohm’s law value from any two known values.
Units includedEnter volts, millivolts, amps, milliamps, microamps, ohms, kiloohms, or megaohms.
Power checkThe tool also calculates watts so you can choose a safe part rating.
Calculator
Results
Voltage
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Current
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Resistance
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Power
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Formulas
Ohm’s law applies to resistive loads and DC approximations where voltage, current, and resistance are steady.
V = I x R
I = V / R
R = V / I
P = V x I
Practical Notes
- Use RMS voltage and RMS current when applying these formulas to purely resistive AC loads.
- Real components have tolerance and temperature drift, so leave margin in power ratings.
- For LEDs, motors, coils, and semiconductors, use the part’s datasheet model rather than assuming fixed resistance.