Resistor Calculator

Category: Physics
- March 21, 2025
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Calculate resistor values using color bands or determine the color bands for a given resistance value. This calculator supports 4-band, 5-band, and 6-band resistors with temperature coefficients.

Select Operation

Resistor Type

Options

About Resistor Color Codes

Resistors use color bands to indicate their resistance value, tolerance, and sometimes temperature coefficient. The standard color code system helps engineers and technicians identify resistor values without using measuring equipment.

Color Code Chart
Color Digit Value Multiplier Tolerance Temp. Coeff. (ppm/°C)
Black 0 ×1 - -
Brown 1 ×10 ±1% 100
Red 2 ×100 ±2% 50
Orange 3 ×1,000 - 15
Yellow 4 ×10,000 - 25
Green 5 ×100,000 ±0.5% -
Blue 6 ×1,000,000 ±0.25% 20
Violet 7 ×10,000,000 ±0.1% 10
Grey 8 ×100,000,000 ±0.05% 5
White 9 ×1,000,000,000 - 1
Gold - ×0.1 ±5% -
Silver - ×0.01 ±10% -
Types of Resistors by Band Count
  • 4-Band Resistors: Most common type with two significant digits, a multiplier, and a tolerance band
  • 5-Band Resistors: Higher precision resistors with three significant digits, a multiplier, and a tolerance band
  • 6-Band Resistors: Highest precision with three significant digits, a multiplier, a tolerance band, and a temperature coefficient band
Reading Resistor Color Bands

To read a resistor's value:

  1. Orient the resistor with the tolerance band (gold/silver/etc.) to the right
  2. Read the color bands from left to right
  3. For 4-band resistors: First two bands are digits, third is multiplier, fourth is tolerance
  4. For 5-band resistors: First three bands are digits, fourth is multiplier, fifth is tolerance
  5. For 6-band resistors: Like 5-band, with the sixth band indicating temperature coefficient
Temperature Coefficient

The temperature coefficient (in ppm/°C) indicates how much the resistance changes with temperature:

  • A lower value means more stability across temperature changes
  • Only found on high-precision 6-band resistors
  • Calculated as: ΔR/R = α × ΔT where α is the temperature coefficient

What Is the Resistor Calculator?

The Resistor Calculator is a practical tool that helps you determine a resistor's value based on its color bands, or vice versa. It supports standard 4-band, 5-band, and 6-band resistors, making it easy to decode resistance values without the need for manual charts or electrical measuring tools.

Whether you're identifying a resistor in a circuit or planning components for a new project, this calculator simplifies the process and improves accuracy.

Key Features

  • Convert color bands to resistance values instantly
  • Find correct color bands for a specific resistance value
  • Support for 4-band, 5-band, and 6-band resistors
  • Includes tolerance and temperature coefficient options
  • Visual resistor diagram for easier understanding
  • Step-by-step breakdown of each calculation

How to Use the Calculator

You can choose between two main operations:

1. Colors to Resistance Value

  • Select "Colors to Resistance Value" at the top
  • Pick the resistor type (4, 5, or 6 bands)
  • Use the dropdowns to select each color band
  • Click "Calculate" to view the resistance, tolerance, and (if applicable) temperature coefficient

2. Resistance Value to Colors

  • Select "Resistance Value to Colors"
  • Enter the resistance value and unit (Ω, kΩ, or MΩ)
  • Choose the tolerance and temperature coefficient (if needed)
  • Click "Calculate" to see the matching color bands

Formula for Resistor Calculation

4-Band Resistor:
R = (D1 × 10 + D2) × Multiplier ± Tolerance%
5-Band / 6-Band Resistor:
R = (D1 × 100 + D2 × 10 + D3) × Multiplier ± Tolerance%
(6-Band includes an additional temperature coefficient in ppm/°C)

Why This Tool Is Useful

This calculator helps you quickly verify resistor values without the need for decoding charts or formulas by hand. It's especially useful when:

  • Working on electronics repairs or builds
  • Learning electronics and practicing resistor identification
  • Checking the accuracy of resistors in your parts collection
  • Teaching students about resistor color codes and value interpretation

Frequently Asked Questions (FAQ)

What do the color bands mean?

Each color represents a digit, a multiplier, or a tolerance. In 6-band resistors, there's also a temperature coefficient band.

What’s the difference between 4, 5, and 6-band resistors?

  • 4-Band: 2 digits, multiplier, and tolerance
  • 5-Band: 3 digits, multiplier, and tolerance
  • 6-Band: Same as 5-band with an extra band for temperature coefficient

What is a temperature coefficient?

It shows how much the resistance value changes with temperature, measured in ppm/°C (parts per million per degree Celsius). Lower values mean more stability.

Do I need to know all resistor codes?

No. This calculator is designed so you don’t have to memorize anything. Just select or input what you know, and it does the rest.

Can I visualize the resistor?

Yes. The calculator provides a visual representation based on your selections, which helps with learning and validation.

Final Notes

The Resistor Calculator saves time and removes the guesswork when working with resistors. It's an efficient solution for anyone involved in electronics—from beginners to professionals.