Pick what to solve: voltage from I and R, current from V and R, or resistance from V and I.
Depending on the mode, the page computes V = I×R, I = V÷R, or R = V÷I. The two quantities you type must be positive so the third is finite and physically typical for this quick helper.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.