Resistor Calculator

Category: Physics
- May 14, 2025
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Calculate resistor values using colour bands or determine the colour 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 Colour Codes

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

Colour Code Chart
Colour 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 Colour Bands

To read a resistor's value:

  1. Orient the resistor with the tolerance band (gold/silver/etc.) to the right
  2. Read the colour 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 designed to make working with resistors easier. It allows you to calculate resistor values using colour bands or to find the colour bands for a specific resistance value. With support for 4-band, 5-band, and 6-band resistors, this calculator simplifies what can often be a confusing process for both beginners and experienced users alike.

How to Use the Calculator

You can choose between two main operations: converting colours to resistance values or converting resistance values to colours. In the first option, you select the colour bands on the resistor and the calculator will give you the resistance value. In the second option, simply enter a resistance value, and the calculator will show you the corresponding colour bands. This flexibility makes it suitable for various projects and needs.

Types of Resistors Supported

  • 4-Band Resistors: Commonly used, featuring two digits, a multiplier, and a tolerance band.
  • 5-Band Resistors: Provide higher precision with three digits, a multiplier, and a tolerance band.
  • 6-Band Resistors: Offer the highest accuracy, including three digits, a multiplier, a tolerance band, and a temperature coefficient band.

Calculating Resistor Values

When calculating resistor values, the colours on the bands represent specific digits and multipliers. For example, the first two bands denote the significant digits, the third band shows the multiplier, and the last band indicates the tolerance. This system allows for quick and accurate readings without needing additional tools.

Finding Colour Bands for a Resistance Value

If you already know the resistance value but need the colour bands, the calculator can help here as well. You can enter the resistance value, and it will generate the corresponding colour bands for you. This can be particularly useful when designing circuits or replacing components.

Additional Features of the Calculator

  • Tolerance Settings: The calculator allows you to select different tolerance levels, ensuring precise calculations.
  • Temperature Coefficient: For higher precision resistors, you can also include the temperature coefficient, vital for certain applications.
  • Visualisation Options: The calculator can visually display the resistor, making it easier to understand the colour band layout.

Exploring Resistor Colour Codes

The resistor colour code is a universally accepted system that helps you determine the resistor values at a glance. Each colour corresponds to a specific digit or multiplier. Knowing how to read these codes can save time and reduce errors when working on electronic projects.

Why This Calculator is Indispensable

This Resistor Calculator is a valuable resource for anyone working with electronics. Whether you're a student learning the basics or a professional engineer, having this tool on hand can make your work quicker and more efficient. Its user-friendly design and versatile features cater to a wide range of users, making it an essential addition to your toolkit.