Ohm's Law
Solve for
Pick the quantity to find; it becomes the auto field. Enter the other two.
Result
How to use this calculator
Ohm's law, V = I × R, relates the three fundamental DC quantities of a circuit. Choose which quantity you want to find — the matching field turns into an auto field — and the calculator solves it from the other two in real time, also reporting the resulting power. V is voltage in volts (the electrical pressure that pushes charge), I is current in amperes (the flow of that charge), and R is resistance in ohms (the opposition to the flow).
What it means in a real circuit
Every basic circuit analysis starts here. Given a supply voltage and a load resistance you can predict the current that will flow — which tells you whether a wire, fuse or component is sized correctly. Conversely, if you measure the voltage across and current through an unknown component you can find its resistance. Because P = V·I follows directly, part power ratings and the voltage drop across connections are immediate consequences, which is why this is the single most-used relationship in all of electronics.