Ohm's Law Calculator
The definitive tool for electrical engineering. Calculate Voltage, Current, and Resistance instantly.
Circuit Parameters
Calculated Value
What is Ohm's Law Calculator?
Ohm's Law is the most important relationship in electrical engineering. It states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R).
Expressed as V = I × R, it allows you to determine exactly how much current will flow through a component or how much resistance is needed to protect a sensitive device from being damaged by excess electricity.
How to Use
Voltage (V)
The electrical pressure. To calculate it, select "Voltage" and enter Current and Resistance.
Current (I)
The flow rate of electrons. Select "Current" and enter Voltage and Resistance.
Resistance (R)
The opposition to flow. Select "Resistance" and enter Voltage and Current.
Financial Education
The Power of Ohms
A simple way to remember Ohm's Law is the "Water Pipe Analogy":
Voltage is like the water pressure pushing through a pipe.
Current is like the actual flow rate of the water.
Resistance is like the size of the pipe (narrow pipe = more resistance).
Safety & The Human Body
The human body is resistant but not "insulating." While 9V might feel like a tingle on the tongue, 120V can push enough current through your body to be fatal. Resistance drops significantly when your skin is wet, which is why working with electricity in wet conditions is extremely dangerous.
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Frequently Asked Questions
Common questions about this calculator
Why is the unit for Current 'I'?
It stands for "Intensité de courant" (current intensity), a term coined by Frenchman André-Marie Ampère, for whom the Ampere unit is named.
What happens if resistance is zero?
If R = 0, current becomes infinite (a "short circuit"). This causes wires to heat up rapidly and leads to electrical fires, which is why fuses and circuit breakers exist.
Does Ohm's Law apply to AC?
Partially. For simple resistive loads like a heater, it works. For complex things like motors (inductive) or capacitors, we use "Impedance" (Z) instead of simple resistance.
Is Ohm's Law a "Law" or "Rule"?
It's an empirical relationship that holds true for most materials at constant temperatures, but non-ohmic materials (like LEDs or transistors) behave differently.