Solve voltage, current, resistance and power from any two known values.
Ohm's Law (V = I × R) and the Power Law (P = V × I) together define the four electrical quantities. Any two quantities uniquely determine the other two. The calculator solves all six possible input pairs: V+I, V+R, V+P, I+R, I+P, R+P. Edge cases like zero voltage, zero current or zero resistance are flagged explicitly because they indicate open or short circuits where some quantities are undefined or infinite.
Ohm's Law
Voltage = Current × Resistance
Power Law
Power = Voltage × Current = Current² × Resistance = Voltage² ÷ Resistance
Ohm's Law states that the voltage across a resistor is directly proportional to the current flowing through it, with the resistance as the constant of proportionality: V = I × R.
There are four variables (V, I, R, P). Choosing any two gives a unique solution for the other two: C(4,2) = 6 combinations. This calculator handles all six.
Zero resistance is an ideal short circuit. Ohm's Law says current would be infinite (V ÷ 0), which is a real circuit fault. The calculator flags this rather than returning Infinity.
For pure resistive loads, yes. AC circuits with capacitors or inductors have impedance (Z), not just resistance, and require phasor math. This calculator covers the resistive case.