Ohm’s Law

Choose two known quantities. The missing value and DC power update immediately: V = I·R and P = V·I. Example: 12 V and 6 Ω give 2 A and 24 W.

This calculator uses nonnegative voltage/current magnitudes for an ideal ohmic DC load. Input resistance must be positive. With known V and I, I must be positive; V = 0 can then yield the limiting result R = 0. With a known positive resistance, zero voltage or current gives zero power. It does not model AC impedance, temperature changes or non-ohmic components.

Decimal comma, point and scientific notation are accepted. Very small and large outputs use scientific notation; an unrepresentable overflow or positive underflow produces an error instead of infinity or a false zero. Each known pair keeps its own drafts through navigation and reload.