Ohm's Law Calculator
Enter any two of voltage(V), current(I), resistance(R), power(P) to calculate the rest. (V=IR, P=VI)
Enter Values (2 or more)
Enter any two or more of the four values to automatically calculate the rest.
The Ohm's law calculator takes any two of voltage (V), current (I), resistance (R), and power (P) and automatically computes the rest, based on V=IR and P=VI.
The formulas
V=IR (voltage = current × resistance), I=V/R (current = voltage ÷ resistance), R=V/I (resistance = voltage ÷ current), and power can be expressed multiple ways as P=VI=I²R=V²/R. Knowing any two values lets you derive the other two.
Frequently Asked Questions
Can the other values really be found from just two?
Yes — knowing any two of V, I, R, and P lets you combine Ohm's law and the power formula to compute the remaining two.
What happens to current as resistance increases?
At constant voltage, current decreases inversely as resistance increases (I=V/R).
Are power (W) and energy (kWh) the same thing?
Power is the instantaneous rate of energy consumption (W), while energy is power multiplied by time used, giving total energy consumed (Wh, kWh) — they're different concepts.
Do these formulas apply to AC circuits too?
For purely resistive circuits, they apply directly using RMS values, but circuits with inductors or capacitors require accounting for impedance and phase difference.
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