Enter any two of voltage, current, resistance and power, and calculate the other two. All four values and the formulas used are shown.
Enter any two values and leave the other two blank.
Ohm's law states that voltage equals current multiplied by resistance (V = I × R), and electrical power equals voltage multiplied by current (P = V × I). Combining those two relationships lets any two known values determine the other two. Exactly two fields should be filled in: leaving fewer than two, or filling in three or four, returns an error so that an inconsistent set of values is never silently used. Results assume simple DC or resistive behaviour.
What are the Ohm's law formulas? The core formulas are V = I × R and P = V × I. Rearranged forms include I = V / R, R = V / I, P = I² × R and P = V² / R, and the calculator shows the values from whichever pair was entered.
Why does the calculator require exactly two values? Two values are enough to determine the other two. Entering three or four risks an inconsistent set that does not satisfy Ohm's law, so the calculator asks for exactly two instead of choosing silently.