Ohm's Law Calculator
Enter any two values — voltage, current, and resistance — to calculate the rest, including power.
About the Ohm's Law Calculator
The Ohm's Law Calculator finds voltage, current, resistance and power. Enter any two of the values and the tool calculates the others. It is useful for electronics students, hobbyists and anyone designing simple circuits.
Ohm's law states that voltage (V) equals current (I) times resistance (R). Power (P) equals voltage times current, which also equals I squared times R or V squared divided by R. Voltage is measured in volts, current in amperes, resistance in ohms and power in watts. Choose resistors whose power rating is higher than the calculated power to prevent overheating.
How to use it
- Enter two known values among voltage, current and resistance.
- Press Calculate.
- Read the remaining values and the power.
- Check component ratings.
Tips and good to know
- Convert milliamps to amps by dividing by 1000.
- Use the power result to select a resistor wattage.
- Real components have tolerances.
Frequently asked questions
What is the formula?
V = I × R.
Can it be used for AC?
It applies to resistive AC loads in simple cases.
Is it safe advice for mains work?
Consult a qualified electrician for mains.