🔌 Ohm's Law Calculator (V, I, R, P Wheel)
Enter any two of voltage, current, resistance and power, and the Ohm’s-law wheel gives the other two.
Enter any two of V, I, R, P
V — voltage
12 V
I — current
3 A
R — resistance
4 Ω
P — power
36 W
The Ohm’s-law / power wheel: 12 relations between voltage, current, resistance and power. 🔒 Computed in your browser.
How the ohm's law calculator (v, i, r, p wheel) works
Ohm’s law (V = IR) combines with the power relations (P = VI = I²R = V²/R) into twelve equations linking voltage V, current I, resistance R and power P. Give any two and the tool derives the other two from the right relation.
The all-four-outputs wheel beats a bare V = IR — enter volts and ohms and immediately see current and power. The four power forms are shown so you can see which relation was used.
Frequently asked questions
What is Ohm’s law?
Voltage equals current times resistance: V = IR. It means current through a resistor is proportional to the voltage across it (at constant temperature).
How do I calculate power in a circuit?
Power P = VI, and using Ohm’s law also P = I²R = V²/R. For 12 V across 4 Ω: I = 3 A and P = 36 W. Enter any two of V, I, R, P.
How do I find current from voltage and resistance?
I = V/R. 12 V across 4 Ω gives 3 A. Enter V and R and the tool returns current (and power).
What is the Ohm’s-law wheel?
A chart of the twelve equations relating V, I, R and P, so you can get any two from the other two. This calculator implements the whole wheel.
What units are used?
Volts (V), amperes (A), ohms (Ω) and watts (W). 1 V = 1 A × 1 Ω, and 1 W = 1 V × 1 A.