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How to Read Resistor Color Codes?

Electrical resistors with different bands on a PCB

Table of Contents

What is Resistor Color Code?

The resistor color code is a method for indicating the value, tolerance, accuracy, and usage of colored bands covered at the resistor frame. This color-coding technique permits the easy identification of resistor parameters without having to review a datasheet. Each color represents a specific number, and processing a series of colors provides the resistance value in ohms.

This method of design is frequently utilized in electronics because it is quick and tightly packed, making it excellent for the little resistors found in many circuits. Recognizing the resistor coloration coding is essential for all people running in electronics or electric design.

Bands of Color Code Resistors

Resistor color codes are a set of colored bands painted onto the resistor frame. Each band demonstrates a specific value or function of the resistor, consisting of resistance, tolerance, and, in a few cases, balance or temperature coefficient. Here’s a detailed look at each kind of band found on resistors.

Significant Digit Band

These are the first two or three bands on the resistor. They represent the essential digits of the resistor’s value. These are 4-band resistors, 5-band resistors, and six-band resistors.

Multiplier Band

The multiplier band appears after the significant digit bands and shows the factor by which the significant digits should be multiplied. This band defines the scale of the resistor’s value.

Tolerance Band

The tolerance band indicates how much the real resistance may differ from the reported value. This is usually the final band on a four- or five-band resistor.

Temperature Coefficient Band

The temperature coefficient band displays how much the resistor’s resistance varies with temperature. This is commonly found on precision resistors where temperature stability is critical.

How to Read Resistor Color Codes?

Step-by-Step:

  1. Identify the color bands on the resistor. 
  2. Determine the first and second significant digits using the color code chart.
  3. Find the multiplier from the third band.
  4. Calculate the resistance value by combining the digits and multiplier.
  5. Check the tolerance to understand the range of possible values.

Table 1. Resistor Color Digits and Their Multipliers

Color

Digit

Multiplier

Black

0

0Ω

Brown

1

10Ω

Red

2

100Ω

Orange

3

1kΩ

Yellow

4

10kΩ

Green

5

100kΩ

Blue

6

1mΩ

Violet

7

10mΩ

Grey

8

100mΩ

White

9

1GΩ

Gold

 

0.1Ω

Silver

 

0.01Ω

Table 2: Resistor Colors and Their Tolerance Values

Color

Value

Black

N/A

Brown 

±1% (F)

Red

±2% (G)

Orange

±3%

Yellow

±4%

Green

±0.5% (D)

Blue

±0.25% (C)

Violet

±0.10%

Grey

±0.05%

White

N/A

Gold

±5% (J)

Silver

±10% (K)

Development of Resistor Color Code

In the Nineteen Twenties, the Radio Manufacturers Association (RMA) created the RMA resistor color code as an everlasting resistor coloring code indication. In 1930, the first radios with RMA color-coded resistors were built.

Four-Band Resistor

4 band resistor

Bands and Their Meanings:

  • First Band: This is the first significant digit of the resistance value.
  • Second Band: This is the second significant digit of the resistance value.
  • Third Band: Multiplier, which indicates the power of ten by which the first two digits should be multiplied.
  • Fourth Band: Tolerance, indicating the precision of the resistor.

Example:
For a resistor with color bands: red, violet, yellow, and gold:

  1. First Band (Red): 2 (first significant digit)
  2. Second Band (Violet): 7 (second significant digit)
  3. Multiplier (yellow): ×10^4 (10,000)
  4. Tolerance (Gold): ±5%

Calculation:
27×10,000=270,000
27×10,000=270,000 ohms, or 270 kΩ with a tolerance of ±5%.

Five-Band Resistor

4 band and 5 band resistor color chart

Bands and Their Meanings:

  • First Band: it is the first significant digit of the resistance value.
  • Second Band: It is the second significant digit of the resistance value.
  • Third Band: this is the third significant digit of the resistance value.
  • Fourth Band: Multiplier, which indicates the power of ten by which the first three digits should be multiplied.
  • Fifth Band: Tolerance, indicating the precision of the resistor.

Example:

For a resistor with color bands: brown, black, black, red, and brown:

  1. First Band (Brown): 1 (first significant digit)
  2. Second Band (Black): 0 (second significant digit)
  3. Third Band (Black): 0 (third significant digit)
  4. Multiplier (Red): ×10^2 (100)
  5. Tolerance (Brown): ±1%

Calculation:
100×100=10,000
100×100=10,000 ohms, or 10 kΩ with a tolerance of ±1%.

Six-Band Resistor

six band resistor

Bands and Their Meanings:

  • First Band: it is the first significant digit of the resistance value.
  • Second Band: it is the second significant digit of the resistance value.
  • Third Band: i is the third significant digit of the resistance value.
  • Fourth Band: Multiplier, which indicates the power of ten by which the first three digits should be multiplied.
  • Fifth Band: Tolerance, indicating the precision of the resistor.
  • Sixth Band: Temperature coefficient, which indicates how much the resistance value changes with temperature.

Example:

For a resistor with color bands: brown, green, black, orange, brown, and red:

  1. First Band (Brown): 1 (first significant digit)
  2. Second Band (Green): 5 (second significant digit)
  3. Third Band (Black): 0 (third significant digit)
  4. Multiplier (Orange): ×10^3 (1,000)
  5. Tolerance (Brown): ±1%
  6. Temperature Coefficient (Red): 50°C

Calculation:
150×1,000=150,000
150×1,000=150,000 ohms, or 150 kΩ temperature coefficient of 50 °C.

Table 3. Review of the Bands in a Resistor

 4 Band5 Band6 Band
1st band1st significant digit1st significant digit1st significant digit
2nd band2nd significant digit2nd significant digit2nd significant digit
3rd bandmultiplier3rd significant digit3rd significant digit
4th bandtolerancemultipliermultiplier
5th bandN/Atolerancetolerance
6th bandN/AN/Atemperature coefficient

Practical Tips for Using Resistor Color Codes

Practice:

  • Memorize the Color Chart: Regularly exercise studying the color bands and memorizing the coloration chart.
  • Use Tools: Utilize color code calculators or cellular apps designed to assist in decoding resistor values quickly.
  • Verify with a Multimeter: When doubtful, move-test your reading with a virtual multimeter. Ensure good lighting
  • Proper lighting is essential to distinguish between similar colors, such as pink and brown or blue and violet. Poor lighting fixtures can result in misreading the bands. Double-check your readings.
  • To be safe from errors, double-check your calculations, mainly if the resistor is for use in an important part of a circuit.

Common Mistakes:

  1. Reading Direction: Always start reading from the end, with the band closest to the edge. This is usually the finale, with the tolerance band being the last read.
  2. Color Confusion: Colors may appear different based on the lighting and age of the resistor. When working with comparable colors, use a multimeter to double-check.
  3. Skipping Bands: Make sure to account for all of the resistor’s bands, including any tolerance and temperature coefficient bands that may be present.

Exceptions to Color Code Resistors

5-Band Resistor with the 4th Band of Gold or Silver

In most cases, the fourth band on a 5-band resistor represents the multiplier. However, if the fourth band is gold or silver, it indicates a deviation from the standard coding system. This changes the way you calculate the resistance value.

For example, a 5-band resistor with bands colored red, violet, black, gold, and brown would be interpreted as follows: red (2), violet (7), black (0), gold (×0.1), and brown (±1% tolerance).
The resistance value is calculated as follows:
270×0.1=27
270×0.1=27 ohms with a ±1% tolerance.

This exception is useful for identifying resistors with very low resistance values.

Deviating Resistor Band Colors

Resistor color codes generally follow a standardized system, but there are cases where the colors may deviate due to manufacturing processes, special applications, or custom requirements. Some resistors may use unique color bands that don’t fit the traditional coding. This often happens with high-precision resistors, which might use additional bands to indicate reliability or stability under specific conditions.

Single Black Resistor Band

A resistor with a single black band is known as a zero-ohm resistor. Despite being called a resistor, it functions more like a jumper or a wire, offering negligible resistance, typically less than 0.05 ohms. Zero-ohm resistors are used primarily for circuit board design flexibility.

They allow for easy connection of different traces on a PCB (printed circuit board) without the need for redesign. This can be particularly useful during the prototyping phase or when there’s a need to configure or modify connections without altering the PCB layout. Zero-ohm resistors simplify automated PCB assembly processes as they can be placed by the same machines that place other resistors, maintaining uniformity in the manufacturing process.

Resistance Reliability Band

Some resistors, especially those used in high-reliability applications, feature an additional band that indicates their reliability or failure rate. This is often referred to as the resistance reliability band, or sometimes the quality band. This band is typically seen on precision resistors used in critical applications such as aerospace, medical devices, and military equipment where failure could have significant consequences. The color of this band provides information about the expected failure rate over a specified period,often measured in percentage failures per 1000 hours of operation.

Resistor Color Code Calculator

A resistor color code calculator is a handy tool used to quickly and accurately determine the resistance value of a resistor based on its color bands. These calculators interpret the color bands according to the standard resistor color code and perform the necessary calculations to provide the resistance value in ohms. They are particularly useful when dealing with resistors with multiple bands or when the color bands are difficult to read.

Some best calculators:
Some of the best resistance color code calculators available online include those provided by electronics hobbyist websites such as:

These calculators are user-friendly, reliable, and often include additional features such as tolerance calculation and temperature coefficient interpretation.

Conclusion

Understanding resistor color codes is essential for everybody running electronic circuits. This coding machine, advanced for quick and correct identification, has advanced over decades and has become a staple in electronics due to its efficiency and compactness.

Whether you are dealing with widespread four-band resistors, particularly 5-band resistors, or extraordinarily specialized six-band resistors, knowing how to examine and interpret these coloration codes is critical. Special instances, which include zero-ohm resistors and resistors with reliability bands, spotlight the flexibility and specificity of this machine, making sure that resistors can meet the diverse needs of contemporary electronics.

FAQs

What is the purpose of the tolerance band on a resistor?

The tolerance band on a resistor indicates how much the actual resistance cost can vary from the said value. It indicates the range within which the resistor is guaranteed to perform. For instance, a resistor with a tolerance of ±5% could have an actual resistance that is 5% better or lower than the value indicated by using the color bands.

How do I study a resistor with faded or unclear color bands?

When resistor color bands are dwindled or doubtful, the exceptional method is to use a digital multimeter to determine the actual resistance price. This guarantees accurate identification, mainly if the resistor is important to the circuit’s overall performance. It’s also an amazing exercise to double-check with a multimeter even if the color bands are clear, specifically in critical programs.

Can resistor coloration codes be used for surface-mount resistors (SMD)?

No, surface-mount resistors (SMD) typically no longer use color codes due to their small length. Instead, they use numerical codes printed immediately on the resistor’s surface. These numerical codes suggest the resistance value and, once in a while, the tolerance. For instance, “472”on an SMD resistor method is 4,700 ohms or 4.7 kΩ.

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About the Author
Hadia
With a wealth of experience in PCB, PCBA, and PCB design, I am dedicated to delivering informative and engaging content that empowers readers in the electronics field.
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