Ohm's Law Calculator — Voltage, Current, Resistance & Power
Ohm's Law is the fundamental relationship governing electrical circuits: Voltage equals Current multiplied by Resistance (V = I × R). This calculator solves for any of the three values given the other two, plus calculates power dissipation.
The Four Key Formulas
Voltage: V = I × R
Current: I = V ÷ R
Resistance: R = V ÷ I
Power: P = V × I
Practical Applications
Ohm's Law calculations are essential for selecting correct resistor values in circuits, sizing power supplies, calculating fuse/breaker ratings, and troubleshooting electrical faults — used by electronics hobbyists, students, and professional engineers alike.
Frequently Asked Questions
Does Ohm's Law apply to all electrical components? +
Ohm's Law applies precisely to 'ohmic' components like standard resistors, where resistance stays constant regardless of voltage/current. Non-ohmic components (diodes, transistors, light bulbs at high temperature) have variable resistance and don't follow a simple linear V=IR relationship.
Why is power dissipation important to check? +
Components have maximum power ratings. If actual power dissipation (calculated as P=VI) exceeds a resistor's rated wattage, it will overheat and potentially fail or cause a fire hazard — always verify components are rated for the calculated power.
What's the difference between AC and DC for this calculator? +
This calculator assumes simple DC (direct current) relationships. AC (alternating current) circuits involve additional factors like impedance, frequency, and phase angle, which require more complex calculations beyond basic Ohm's Law.