Ohm’s Law & Power Calculator
Use our definitive Ohm’s Law Calculator to instantly determine voltage, current, resistance, and electrical power. Based on the fundamental principles discovered by Georg Simon Ohm, this tool provides step-by-step formula substitutions for V = IR and power dissipation equations (P = IV) making it perfect for physics students, electrical engineers, and circuit designers.
Enter any two values to calculate the third
Power Dissipation (P)
Understanding Ohm’s Law and Electrical Power
In electrical engineering and physics, Ohm’s Law is a foundational principle formulated by Georg Simon Ohm. It states that the current passing through a conductor between two points is directly proportional to the voltage across the two points. The formula is expressed as:
V = I × R
- V (Voltage): The electrical potential difference causing charges to move, measured in Volts (V).
- I (Current): The steady flow of electrical charge, measured in Amperes (A).
- R (Resistance): The material’s opposition to current flow, measured in Ohms (Ω).
Joule Heating and Electrical Power
When electrical current passes through a simple resistance, electrical energy is converted into heat energy—a process known as Joule heating. The rate of this energy transfer is the Power Dissipation (P), measured in Watts (W). The power can be derived algebraically using three interchangeable formulas depending on the known variables in your DC circuit:
- P = I × V (Best when Current and Voltage drop are known)
- P = I² × R (Helpful for determining power loss in transmission lines)
- P = V² / R (Useful when observing a stable voltage source across a resistor limit)
Our Ohm’s law calculator automatically handles standard SI unit conversions and powers of ten, making circuit analysis, resistor rating selection, and electromagnetism homework straightforward and error-free.