Solve voltage, current, resistance and power — enter any two.
Calculated instantly in your browser.
Understanding your result
Make sure units are consistent: volts, amps, ohms and watts.
Formula and method
V = I × R, P = V × I. From any two quantities the remaining two can be derived (for example R = V ÷ I and P = I² × R).
Worked example
12 V across 2 A gives 6 Ω of resistance and 24 W of power.
How to use this tool
- Enter any two known values.
- Leave the rest blank.
- Press Calculate.
Common mistakes to avoid
- Entering milliamps as amps (1 mA = 0.001 A).
About the Ohm's Law Calculator
Ohm's Law links voltage, current and resistance. Enter any two known values and this calculator finds the others, plus power.
Explore all Science and Engineering tools
Frequently asked questions
How many values do I need?
Exactly two. The calculator derives the remaining quantities from them.