Ohm's Law Calculator
Calculate Voltage (V), Current (I), Resistance (R), and Power (P) across any electrical circuit.
Calculated Electrical Power (Watts)
—
—
How to Calculate Voltage, Current, Resistance & Power
- Enter any two known values among Voltage (V), Current (I), Resistance (R), or Power (P).
- The tool computes the remaining two unknown parameters automatically.
- View results with standard engineering units (Volts, Amperes, Ohms, Watts).
Ohm’s Law & Joule’s Law Equations
-
Ohm’s Law:
V = I × R|I = V / R|R = V / I -
Electrical Power:
P = V × I = I² × R = V² / R
Circuit Worked Example
-
A 12V automotive battery powering a 4Ω speaker:
Current (I) = 12 / 4 = 3.0 Amps.Power (P) = 12 × 3 = 36.0 Watts.
Common Applications
- Designing printed circuit boards (PCB) and breadboard prototypes.
- Sizing automotive electrical fuses and wire gauges.
- Solar power battery inverter sizing.
Frequently Asked Questions
What is Ohm’s Law?
Ohm’s Law states that current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to resistance.
What if resistance is zero?
Zero resistance represents an ideal theoretical short circuit, resulting in infinite current. The calculator prevents zero division.