Ohm's Law Calculator
Enter any 2 of Voltage (V), Current (I), Resistance (R), and Power (P) to instantly calculate the other two. Includes an interactive Ohm's Law wheel, unit conversion, and AWG wire gauge recommendation.
Ohm's Law Calculator
Select exactly 2 values as 'Known' and enter their values. The remaining 2 will be calculated.
Formula Reference
Results
Wire Gauge Recommendation
What is Ohm's Law?
Ohm's Law defines the relationship between Voltage (V), Current (I), and Resistance (R) in an electrical circuit: V = I × R. Combined with the power equation P = V × I, any two of these four quantities can determine the other two. This calculator provides instant bidirectional calculation with unit conversion and practical wire gauge recommendations.
How to Use the Ohm's Law Calculator
- Click 'Known' on any two of the four variables (Voltage, Current, Resistance, Power)
- Enter the values for your two known quantities using the appropriate units
- The calculator instantly computes the remaining two unknown values
- Check the results summary and wire gauge recommendation below
- Use the Ohm's Law wheel diagram as a visual formula reference
Frequently Asked Questions
What formulas does this calculator use?
The calculator uses all Ohm's Law and power formulas: V=IR, I=V/R, R=V/I, P=VI, P=I²R, P=V²/R. Depending on which two values you provide, it selects the appropriate formula to calculate the unknowns.
What is AWG wire gauge and why does it matter?
AWG (American Wire Gauge) is a standardized system for wire sizes. Thicker wires (lower AWG numbers) can safely carry more current. Using an undersized wire causes overheating and potential fire hazards. This calculator recommends the minimum safe gauge for your circuit current.
Can I use this for AC circuits?
Ohm's Law applies to both DC and simple AC circuits. For AC circuits with reactive components (capacitors, inductors), you would use impedance (Z) instead of resistance (R). This calculator is best suited for DC and resistive AC circuits.