Resistor Calculator

Category: Physics
- May 22, 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

Understanding the Resistor Calculator

The Resistor Calculator is a handy tool for electronics enthusiasts. It helps users calculate resistor values based on colour bands. You can also work backward—input a resistance value and find out the corresponding colour bands. This makes it easier to understand and work with different types of resistors.

Types of Resistors You Can Use

With this calculator, you can select from different types of resistors. The most common types include:

  • 4-Band Resistors: These have two digits, a multiplier, and a tolerance band.
  • 5-Band Resistors: These offer higher accuracy with three digits, a multiplier, and a tolerance band.
  • 6-Band Resistors: These are the most precise, featuring three digits, a multiplier, a tolerance band, and a temperature coefficient.

How to Calculate Resistance Value

You can easily determine the resistance value using the colour bands of your resistor. Just select the colours of the bands, and the calculator will do the Math for you. For a 4-band resistor, you choose two colours for the significant digits, one for the multiplier, and one for the tolerance. The calculator will then provide the total resistance value, which is a great way to ensure accuracy in your electronics projects.

Converting Resistance Values to Colours

If you have a specific resistance value, the Resistor Calculator can help you find the corresponding colour bands. Simply input the resistance value, select the tolerance, and the calculator will generate the colours for you. This feature comes in handy for creating custom circuits or working with existing ones where you need to replace resistors.

Visual Representation of Resistors

One of the user-friendly features of this calculator is its visual representation option. When activated, it shows a clear diagram of the resistor with its colour bands. This not only makes it easier to understand your results but also provides a fun way to learn about resistor values visually. Seeing the colours associated with values helps reinforce learning for beginners.

Understanding Tolerance and Temperature Coefficient

The calculator also allows you to choose the tolerance and temperature coefficient for better accuracy. Tolerance indicates how much the actual resistance may vary from the stated value. For example, a resistor with ±5% tolerance can vary by 5% above or below its listed resistance. The temperature coefficient tells you how much the resistance changes with temperature. This is particularly important for high-precision applications.

Advanced Options for Serious Hobbyists

For those who want to dive deeper, the Resistor Calculator offers advanced options. You can choose to show calculation steps and visualize the resistor. These features are particularly beneficial for students and hobbyists who want to learn how to calculate resistor values step-by-step.

Getting Started with Your Resistor Calculations

Using the Resistor Calculator is straightforward. Whether you’re calculating resistance from colour bands or vice versa, the tool caters to all needs. Its clear layout makes it user-friendly, while the advanced features support more complex calculations. With just a few clicks, you can enhance your understanding of resistors and their values in your projects.