Solve for Voltage: 0.5A Through 220Ω
Enter any two of voltage, current, resistance, and power, and the page fills in the other two.
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Result
About this tool
This page opens the Ohm's law calculator with 0.5A of current and a 220Ω resistor already filled in — the voltage and power below are computed live on load, from those two values.
Solving for voltage is what you need when you know how much current a component draws (from a datasheet, or a multimeter reading) and want to know the voltage drop across a resistor in series with it: V = I × R gives 0.5A × 220Ω = 110V. The power dissipated, P = VI, comes out to 55W here — a reminder that this pairing of current and resistance is a large-signal example, not a typical low-voltage hobby circuit.
Because the calculator solves from whichever two fields you fill in, you can just as easily start from a known voltage and resistance instead, or from voltage and power — swap in your own numbers and every other field updates instantly.
Example. Voltage 12 V and resistance 4 Ω return current 3 A and power 36 W. Voltage 9 V and current 20 mA return resistance 450 Ω and power 180 mW.
Limit. At least two of voltage, current, resistance, and power must be strictly positive. A later power-and-resistance step overwrites current and voltage when power is also filled in.