Ohm's Law Calculator — Free Online Calculator
Free Ohm's law calculator. Enter any two values of voltage (V), current (I), resistance (R), or power (P) to find the other two. Includes formulas and reference chart.
How to Use This Calculator
Enter any two known electrical values — voltage (V), current (I), resistance (R), or power (P) — and the calculator will compute the remaining two values using Ohm's Law and the power equation.
The Formula Explained
Ohm's Law states that voltage equals current times resistance: V = I × R. Combined with the power equation P = V × I, you can derive any two unknowns from any two knowns. The 12 key formulas are: V = I×R, V = P/I, V = √(P×R), I = V/R, I = P/V, I = √(P/R), R = V/I, R = V²/P, R = P/I², P = V×I, P = V²/R, P = I²×R.