Ohm's Law Calculator

Solve voltage, current, resistance, and power

Ohm's law describes the relationship between voltage, current, and resistance in a simple electrical circuit. Enter any two of voltage, current, and resistance, and the calculator finds the rest, including power.

Ohm's Law: V = I·R and P = V·I. Choose what to solve, then enter the two known values.

Current (I)

2

A

Power (P)

24

watts

How to Use This Calculator

  1. Choose what you want to solve for (voltage, current, resistance, or power).
  2. Enter the two known values the calculator asks for.
  3. Read the result and the power.

Why Use This Calculator?

  • Choosing the right resistor for an LED or small electronics project.
  • Estimating current draw from a device's voltage and resistance.
  • Checking basic electrical homework.

Real-World Examples

12 volts across 6 ohms

The current is 12 ÷ 6 = 2 amps, and the power is 12 × 2 = 24 watts.

The core relationships

Voltage = current × resistance (V = I × R). Power = voltage × current (P = V × I). So if you know any two of V, I, and R, you can find the third and the power.

Frequently Asked Questions

What do the symbols mean?

V is voltage (volts), I is current (amps), R is resistance (ohms, shown as Ω), and P is power (watts).

Why do I get an error with zero current or resistance?

Because the formula divides by those values, a zero would mean dividing by zero, which isn't defined. Enter a non-zero value.

Does this apply to AC circuits?

Ohm's law in this simple form applies to DC and resistive loads. AC circuits with coils or capacitors need a more complete treatment.

Important Disclaimer

Covers basic DC Ohm's law calculations. Not a substitute for proper electrical design or safety guidance on real circuits.

Privacy

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