Select any two values to calculate the others:
Free online Ohm's Law calculator: calculate voltage (V), current (I), resistance (R), and power (P). Enter any two values to find the others. Perfect for electronics, circuit design, and physics. Mac OS 9 retro style.
Input any two known values from Voltage (V), Current (I), Resistance (R), and Power (P). The calculator works with any combination of two known parameters.
Leave the remaining two fields empty. The calculator automatically determines which values you want to find based on which fields are filled.
Press the Calculate button to compute all unknown values. Results are displayed with 3 decimal precision in volts, amperes, ohms, and watts.
Use the calculated values for circuit design, troubleshooting electronics, physics homework, or electrical engineering projects. Clear to start a new calculation.
Q: What is Ohm's Law?
A: Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. The formula is V = I × R, where V is voltage, I is current, and R is resistance.
Q: How does the power formula relate to Ohm's Law?
A: The power formula P = V × I (watts) is derived from Ohm's Law. Combined with V = I × R, you can derive P = I² × R and P = V² / R, allowing calculation of power from any two known electrical values.
Q: Can I use this for AC circuits?
A: This calculator works for DC circuits and resistive AC circuits. For AC circuits with reactive components (capacitors, inductors), you need to account for impedance and power factor, which this basic calculator does not handle.