Ohm's law calculator
Solve for voltage, current, resistance or power from any two known values.
Ohm's law calculator
Paste one or more lines describing a simple electrical circuit and this calculator fills in what you didn't specify. Give any two of voltage (U), current (I), resistance (R) and power (P) — for example U=12V I=0.5A or R=4.7kΩ P=2W — and it solves the other two using Ohm's law and the power law, one line at a time. Units understood include V, A, Ω (or "ohm") and W, with the milli and kilo prefixes (mV, mA, kΩ, kW, and more), so you can mix a millivolt reading with a kilo-ohm resistor on the same line.
The options bar controls how the result is shown. Significant figures sets how many digits each value is rounded to. Turning on "Show formula used" appends the exact equation applied to that line — R = U / I, P = U² / R, and so on — so the calculation stays auditable rather than a black box. "Include wire loss" adds the power dissipated in a length of wire, given its resistance, which is useful for estimating losses over a cable run once the current is known. Output can be plain text, one line per result, or a table with a header row.
Each line is solved independently, so a batch of measurements can be pasted at once; a line with anything other than exactly two known quantities, or one that would divide by zero, is reported with a plain explanation while every other line still solves. Windows and Unix line endings are both accepted, and the tally below the output shows how many lines were solved.
Everything runs in your browser — nothing you paste is uploaded anywhere. Copy the result, download it as a .txt file, or send it back into the input to adjust a value and recompute.