Resistor Color Code Calculator

Resistor Color Code Calculator is a useful, interactive and modern web application (built with HTML, CSS and JavaScript) that calculates the resistance value of 3, 4, 5, and 6-band resistors.

Try the Resistor Color Code Calculator!

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Interface Preview

A 3-band resistor example showing Brown (1), Black (0), Red (x100Ω) bands resulting in a resistance of 1 KΩ (1000 Ω)].

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Features

• Supports 3, 4, 5, and 6-band resistors.
• Live SVG preview that updates based on user's choices.
• Input validation with error messages.
• Color-coded dropdown borders for visual feedback.
• Automatic unit conversion (Ω → KΩ → MΩ) based on resistance.

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User Guide

1. Select the number of bands.
2. Choose the color for each band from the dropdown menus.
3. Click Calculate to display the resistance value.

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Mathematical Logic

The resistance value is calculated based on the number of bands:

3-Band Resistor:

$$R = (digit_1 \times 10 + digit_2) \times multiplier$$

4-Band Resistor:

$$R = (digit_1 \times 10 + digit_2) \times multiplier \pm tolerance$$

5-Band:

$$R = (digit_1 \times 100 + digit_2 \times 10 + digit_3) \times multiplier \pm tolerance$$

6-Band:

$$R = (digit_1 \times 100 + digit_2 \times 10 + digit_3) \times multiplier \pm tolerance$$ $$\text{+ Temperature Coefficient (ppm/K)}$$

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Glossary of Terms

• Resistance: The measure of the opposition to the flow of electric current within a circuit, measured in Ohms (Ω).
• Band: A colored ring painted on the body of a resistor, representing a specific numerical value, multiplier, or tolerance.
• Significant Digit: The primary numbers derived from the first two (or three) bands, which form the base value of the resistor.
• Multiplier: The factor by which the significant digits are multiplied to determine the total resistance in Ohms ($\Omega$).
• Tolerance: The acceptable percentage by which the actual resistance is allowed to deviate from its stated nominal value.
• Temperature Coefficient: The rate at which the resistance value changes in response to temperature variations, typically measured in ppm/K.
• ppm/K: Parts per million per Kelvin. A unit denoting how many millionths of an Ohm the resistance will change for each degree Kelvin (or Celsius) change in temperature.

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Built With

• HTML
• CSS
• JavaScript

Project Structure

• index.html: The main structure, UI layout, and SVG layout.
• style.css: Styling, transitions, and responsive design.
• script.js: Core logic for calculations, UI toggling, and validation.

Acknowledgements

• Fonts by Google Fonts (DM Sans & DM Mono)

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License

MIT License: Free to use, modify, and distribute with attribution.

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Developer

Dimitrios Poulos
Electrical & Computer Engineering Student

• Release Date: March 2026