Enter any two known values and leave the other two blank.
Free Ohm's Law Calculator
Solve for voltage, current, resistance, or power given any two values.
Ohm's Law is the foundational relationship in basic circuit analysis. Combined with the power equation, any two of the four values (V, I, R, P) let you solve for the other two — this calculator lets you enter any two and computes all four.
Worked Example
Example: 12V across a 4Ω resistor: Current = 12/4 = 3A, Power = 12×3 = 36W.
Formula / Method
V = I × RP = V × I
All other forms (I=V/R, R=V/I, etc.) derived from these two.
Worked Example
Example: 12V across a 4Ω resistor: Current = 12/4 = 3A, Power = 12×3 = 36W.
Formula / Method
V = I × RP = V × I
All other forms (I=V/R, R=V/I, etc.) derived from these two.