Ohm's Law Calculator

Category: Physics
- March 21, 2025
| |

Calculate voltage, current, resistance, and power using Ohm's Law. This calculator allows you to find any of the four values when you know at least two of the others.

Select What You Want to Calculate

Options

About Ohm's Law

Ohm's Law is a fundamental principle in electrical engineering that describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit.

The Basic Formulas
  • Voltage: V = I × R
  • Current: I = V / R
  • Resistance: R = V / I
Power Calculations

Power (P) is the rate at which energy is transferred in an electrical circuit.

  • Power from voltage and current: P = V × I
  • Power from voltage and resistance: P = V² / R
  • Power from current and resistance: P = I² × R
Units
  • Voltage (V): Measured in volts (V)
  • Current (I): Measured in amperes (A)
  • Resistance (R): Measured in ohms (Ω)
  • Power (P): Measured in watts (W)
Applications of Ohm's Law

Ohm's Law is used in many aspects of electrical engineering and electronics:

  • Circuit Design: Determining component values for electronic circuits
  • Troubleshooting: Identifying faults in electrical systems
  • Power Management: Calculating power requirements for electrical devices
  • Battery Life: Estimating how long a battery will last in a circuit
  • Safety: Calculating safe current levels for wires and components

What Is the Ohm's Law Calculator?

The Ohm's Law Calculator is a practical tool that helps you calculate key electrical values—voltage (V), current (I), resistance (R), and power (P)—based on Ohm’s Law. If you know any two of these quantities, the calculator determines the other two for you.

Ohm's Law Formulas:
  • Voltage (V) = Current (I) × Resistance (R)
  • Current (I) = Voltage (V) ÷ Resistance (R)
  • Resistance (R) = Voltage (V) ÷ Current (I)
  • Power (P) = Voltage (V) × Current (I)
  • Power (P) = Voltage² (V²) ÷ Resistance (R)
  • Power (P) = Current² (I²) × Resistance (R)

How to Use the Calculator

Using the calculator is simple. Just follow these steps:

  • Select what you want to calculate: Choose between Voltage, Current, Resistance, or Power.
  • Enter known values: Provide any two required values using the provided input fields and select the correct units (e.g., V, A, Ω).
  • Adjust options if needed: Choose the number of decimal places or enable visual aids like circuit diagrams and calculation steps.
  • Click “Calculate”: The tool will instantly compute and display the missing values.
  • Use “Reset”: Start a new calculation by clearing all inputs.

Why This Calculator Is Useful

This tool simplifies electrical calculations, helping you save time and reduce errors. Whether you're a student, hobbyist, or professional, it can assist with:

  • Learning how voltage, current, resistance, and power relate
  • Designing or analyzing circuits
  • Verifying your work during lab sessions or projects
  • Ensuring safe levels of power and current in your components
  • Estimating battery usage and efficiency in devices

Features

  • Instant calculation of voltage, current, resistance, and power
  • Multiple input unit options (e.g., mA, kΩ, mV)
  • Visual circuit diagram generation
  • Step-by-step breakdown of calculations
  • Customizable decimal precision

Frequently Asked Questions (FAQ)

Do I need to understand Ohm’s Law to use this calculator?

No. The calculator does the math for you. You just need to know two values to get started.

Can I use this for both simple and more advanced circuits?

This tool works best for single-loop (series) DC circuits. For complex circuits, manual analysis may still be needed.

Is the unit conversion automatic?

You choose the input units, and the calculator converts them automatically into base units for accurate results.

Can I visualize the circuit?

Yes. Enable the "Show Circuit Diagram" option to see a basic visual representation of the circuit based on your inputs.

What if I enter incorrect or incomplete values?

The calculator will prompt you to fix any missing or invalid inputs before continuing.

Can this help with schoolwork or exam prep?

Absolutely. It’s a great way to check your answers, learn through the step-by-step breakdown, and better understand circuit relationships.

Final Thoughts

The Ohm's Law Calculator is a practical, easy-to-use tool that helps you work smarter with electrical values. Whether you’re learning, building, or troubleshooting, it provides accurate answers and visual clarity in seconds.