Ohm’s Law Calculator
Calculate voltage, current, resistance, and power instantly. Enter any two known values to solve the entire circuit using Ohm’s Law and Watt’s Law formulas.
Circuit Parameters
Enter any two known values to solve the rest
Potential difference across the circuit
Flow of electric charge
Opposition to current flow
Rate of energy transfer
Circuit Solution
Calculated electrical parameters
Enter any two electrical values above, then click Calculate Circuit to solve for the missing parameters.
Ohm’s Law & Power Formulas
The fundamental equations used to solve DC circuit parameters.
| Quantity | Primary Formula | Alternative Forms |
|---|---|---|
| Voltage (V) | V = I × R | V = P / I, V = √(P × R) |
| Current (I) | I = V / R | I = P / V, I = √(P / R) |
| Resistance (R) | R = V / I | R = V² / P, R = P / I² |
| Power (P) | P = V × I | P = V² / R, P = I² × R |
Ohm’s Law FAQ
Everything you need to know about electrical circuit calculations and fundamentals.
Ohm’s Law is a fundamental principle in electronics that states the current through a conductor between two points is directly proportional to the voltage across the two points. It is expressed by the formula V = I × R, where V is voltage, I is current, and R is resistance.
Simply enter any two of the four electrical parameters (Voltage, Current, Resistance, or Power) into the calculator. You can also select the appropriate unit for each input. The calculator will instantly compute the remaining two values using Ohm’s Law and the power formulas.
Electrical power (P) is the rate at which electrical energy is transferred. The basic formula is P = V × I. By substituting Ohm’s Law (V = I × R), you can derive alternative power formulas: P = I² × R and P = V² / R. This calculator uses all three to solve for missing values.
Ohm’s Law applies to AC circuits, but with a modification. In AC circuits, resistance is replaced by impedance (Z), which includes resistance, capacitance, and inductance. The formula becomes V = I × Z. For purely resistive AC circuits, standard Ohm’s Law (V = I × R) applies perfectly.
The standard SI units are: Volts (V) for voltage, Amperes (A) for current, Ohms (Ω) for resistance, and Watts (W) for power. This calculator supports common multiples like millivolts (mV), kilo-ohms (kΩ), and kilowatts (kW), automatically converting them to base units for calculation.