Ohm's Law Calculator
Enter any two of voltage, current, resistance, and power to solve the other two instantly with Ohm's law.
Processed locally in your browser — nothing is uploaded.
Ohm's Law Calculator
Enter any two values — the other two are solved from V = I·R and P = V·I.
Enter exactly two of the four values.
Formulas: V = I·R · P = V·I · P = I²·R · P = V²/R. Applies to DC and resistive AC loads.
About Ohm's Law Calculator
A four-way Ohm's law solver: type any two of V, I, R, and P and the remaining two are computed from V = I·R and P = V·I. The entered values stay highlighted so you can see at a glance which numbers were yours.
Common uses
- Find the resistance needed to limit current in a simple circuit
- Work out how many amps a heating element draws from its wattage
- Convert between watts and amps for a known supply voltage
Example
Input
V = 12 V, R = 6 Ω
Output
I = 2 A, P = 24 W
Limitations
- Assumes DC or purely resistive AC loads — reactive loads need power-factor math.
Frequently asked questions
What is the Ohm's law formula?
V = I × R: voltage equals current times resistance, with power following as P = V × I. Because the four quantities are linked, entering any two lets the calculator solve the remaining two.
How do I convert watts to amps?
Divide power by voltage: I = P ÷ V. A 1200 W appliance on a 120 V supply draws 10 A — enter the wattage and voltage and the calculator returns the current and equivalent resistance.
Are the electrical values I enter stored or sent anywhere?
No. The calculation runs entirely in your browser and nothing you type is transmitted, logged, or saved.
Does Ohm's law work for AC circuits?
Only for purely resistive loads like heaters and incandescent lamps. Motors, transformers, and electronics are reactive, so real AC analysis needs impedance and power factor rather than plain resistance.
Why do I have to enter exactly two values?
Two known quantities fully determine the other two through V = I·R and P = V·I; a third input could contradict the first two. The calculator keeps your entered values highlighted so you can see which numbers were yours.