Free Online Tools

Ohm's Law Calculator

Choose what to calculate, select a formula, then enter values

Enter Values

Using: V = I × R

Result

Ready to Calculate

Enter both values to see the result

``

Quick Examples

What is Ohm's Law?

Ohm's Law is a fundamental principle in electrical engineering and physics that describes the relationship between voltage, current, and resistance in an electrical circuit. Named after German physicist Georg Ohm, this law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

The basic formula is expressed as V = I × R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms. This simple yet powerful equation forms the foundation for understanding and analyzing electrical circuits.

How to Use This Calculator

1

Choose What to Calculate

Click on one of the tabs (Voltage, Current, Resistance, or Power) to select what you want to find

2

Select the Right Formula

Pick the formula based on which values you already know (e.g., if you have voltage and current, choose the appropriate formula)

3

Enter Your Values

Input the two required values and see the result instantly - no button clicking needed!

Available Formulas

Calculate Voltage

V = I × R
Using Current and Resistance
V = P ÷ I
Using Power and Current
V = √(P × R)
Using Power and Resistance

Calculate Current

I = V ÷ R
Using Voltage and Resistance
I = P ÷ V
Using Power and Voltage
I = √(P ÷ R)
Using Power and Resistance

Calculate Resistance

R = V ÷ I
Using Voltage and Current
R = V² ÷ P
Using Voltage and Power
R = P ÷ I²
Using Power and Current

Calculate Power

P = V × I
Using Voltage and Current
P = V² ÷ R
Using Voltage and Resistance
P = I² × R
Using Current and Resistance

Common Applications

Electronics Design

Engineers use Ohm's Law to design circuits, select appropriate components, and ensure safe current levels throughout electronic devices.

Home Electrical Systems

Electricians apply Ohm's Law to calculate wire sizes, circuit breaker ratings, and power consumption for household appliances.

Troubleshooting Circuits

Technicians use Ohm's Law to diagnose problems in electrical systems by measuring and comparing expected versus actual values.

Frequently Asked Questions

What units are used in Ohm's Law?

Voltage is measured in volts (V), current in amperes or amps (A), resistance in ohms (Ω), and power in watts (W). This calculator handles all standard unit conversions automatically.

How do I use the calculator?

First, select the tab for what you want to calculate. Then choose the formula based on which values you have. Enter the two required values and the result will appear automatically!

Which formula should I choose?

Choose the formula based on what values you already know. Each formula button shows which values it needs, making it easy to pick the right one.

Is this calculator accurate for AC circuits?

This calculator is designed for DC circuits and resistive AC circuits. For AC circuits with reactive components (capacitors and inductors), you would need to consider impedance rather than simple resistance.