Ohm's Law Calculator
What is Ohm's Law?
Ohm's Law is one of the most fundamental principles in electronics and electrical engineering. It describes the relationship between voltage, current, and resistance in an electrical circuit. The law, named after German physicist Georg Ohm, states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points.
The law is expressed by the simple and powerful formula:
V = I × R
How to Use the Calculator
- Select the value you wish to calculate (Voltage, Current, or Resistance) from the dropdown menu.
- The calculator will disable the input field for that value.
- Enter the two known values into the active fields.
- The result for the unknown value will be calculated and displayed automatically.
The Components of Ohm's Law
To use the calculator, it is helpful to understand the three variables involved.
| Variable | Symbol | Unit | Description |
|---|---|---|---|
| Voltage | V | Volts (V) | The electrical potential difference between two points in a circuit. It can be thought of as the "pressure" that pushes electric charge. |
| Current | I | Amperes (A) | The rate of flow of electric charge. It is the amount of charge that passes a point in the circuit per unit of time. |
| Resistance | R | Ohms (Ω) | A measure of the opposition to the flow of current. The higher the resistance, the more difficult it is for current to flow. |
Solving for Each Variable
By rearranging the Ohm's Law formula, you can solve for any of the three variables. Below are examples for each case.
To find Voltage (V)
This is the standard form of the equation. You use it when you know the current and resistance.
| Formula | Voltage = Current × Resistance or V = I × R |
| Example Question | If a circuit has a current of 2 Amperes (A) and a resistance of 6 Ohms (Ω), what is the voltage? |
| Calculation | V = 2A × 6Ω |
| Result | The voltage is 12 Volts. |
To find Current (I)
Use this form when you know the voltage and resistance.
| Formula | Current = Voltage / Resistance or I = V / R |
| Example Question | If a power source provides 12 Volts (V) across a resistor of 24 Ohms (Ω), what is the current? |
| Calculation | I = 12V / 24Ω |
| Result | The current is 0.5 Amperes. |
To find Resistance (R)
Use this form when you know the voltage and current.
| Formula | Resistance = Voltage / Current or R = V / I |
| Example Question | If a component draws 0.5 Amperes (A) when connected to a 12 Volt (V) power supply, what is its resistance? |
| Calculation | R = 12V / 0.5A |
| Result | The resistance is 24 Ohms. |