Electrical and electronics
Ohm’s law and power calculator
Enter any two of voltage, current, resistance and power to get the other two, with SI prefixes such as mA, kΩ and µW.
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Showing the worked example. Results update as you type.
Result
- V = I × R and P = V × I = I² × R = V² / R, for DC or for RMS values in a purely resistive AC circuit.
Method and limits
Ohm’s law relates voltage V, current I and resistance R: V = I R. Power is P = V I, so also P = I² R = V² / R. Any two known quantities fix the other two; the six combinations are solved directly (for R and P: V = √(P R), I = √(P / R)).
Worked example: 12 V across 6 Ω drives 2 A and dissipates 24 W.
Assumptions and limits
The relation holds for DC and, with RMS values, for purely resistive AC loads. With inductance or capacitance use impedance and the power factor; for semiconductors (diodes, LEDs) resistance depends on the operating point, so use the device’s curve instead.
References
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