Ohm’s Law Calculator
Enter any two known values to solve voltage, current, resistance, and power.
V = I × R P = V × ICalculations stay in your browser. Share links contain the input values you choose to share.
How to use this calculator
- Choose the two quantities you know.
- Enter positive values and their engineering units.
- Read all four quantities: voltage, current, resistance, and power.
- Choose another pair to work backward from a different set of known values.
A quick worked example
A 12 V source across a 1 kΩ resistor produces 12 mA of current. The resistor dissipates 144 mW of power. Choose a real resistor rating with an appropriate margin for your application.
A few useful answers
Which pairs of values can I enter?
Voltage and resistance, voltage and current, current and resistance, voltage and power, current and power, or resistance and power.
Does this work for AC circuits?
This tool assumes a DC resistive load. RMS values can be used for a purely resistive AC load, but reactive circuits require impedance and phase calculations.
Why are zero and negative values rejected?
This calculator works with positive magnitudes and finite resistances. Signed circuit analysis, short circuits, and open circuits need separate handling.
Model & assumptions: DC resistive model. Values are positive magnitudes; this tool does not model reactance, phase, or nonlinear components.
Electronics Tools & Calculator
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