Ohm’s Law & Basic Circuit Calculator

Calculate Voltage, Current, Resistance, and Power.

Updated: November 2025 • Free Tool

Enter Any Two Values

V
A
Ω
W
Enter any 2 known values to calculate the other 2.

Results

Power Output
-
Voltage (V) -
Current (I) -
Resistance (R) -

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 electrical circuits.

It states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.

To understand energy transfer in circuits, check out our Work–Energy–Power Calculator.

To calculate forces between charges (Coulomb's Law relates to Force), explore our Forces & Newton's Laws Calculator.

Formulas

  • V = I * R
  • I = V / R
  • R = V / I
  • P = V * I
  • P = I² * R
  • P = V² / R

Key Concepts

  • Linear Relationship: Voltage and current maintain proportionality through constant resistance.
  • Power Dissipation: Electrical power is consumed as heat in resistive elements.
  • Circuit Analysis: Essential for designing and troubleshooting electrical circuits.

How to Use This Calculator

1

Enter Any Two

Input any 2 known values (V, I, R, or P).

2

Calculate

Click Calculate for instant results.

3

View All Values

Get V, I, R, and P simultaneously.

Benefits of Using This Calculator

  • Complete Solution: Calculates all 4 variables from any 2 inputs.
  • Quick Design: Perfect for circuit design and component selection.
  • Educational: Ideal for electronics students and hobbyists.

Factors Affecting Results

  • Temperature: Resistance changes with temperature in most materials.
  • Material Properties: Different conductors have different resistivities.
  • Non-Ohmic Components: Some devices (LEDs, diodes) don't follow Ohm's Law.
Ohm's Law Calculator - V=IR circuit analysis
Ohm's Law Calculator interface for calculating Voltage, Current, Resistance, and Power.

Frequently Asked Questions (FAQ)

Q: What is Ohm's Law?

A: Ohm's Law states that the current passing through a conductor between two points is directly proportional to the voltage across the two points. Formula: V = I * R.

Q: What are the units used?

A: Voltage (V) is measured in Volts (V), Current (I) in Amperes (A), Resistance (R) in Ohms (Ω), and Power (P) in Watts (W).

Q: How is Power related to Ohm's Law?

A: Electrical Power (P) is the rate at which electrical energy is transferred. It can be calculated as P = V * I.