What are Resistor Color Codes?
Resistor color codes are one of the standardized systems used to indicate the resistance value, tolerance, and sometimes reliability or failure rate of resistors using colored bands. The color bands printed on the body of cylindrical resistors help engineers and technicians to identify the resistor’s specifications without needing extra equipment. This color coding is useful for circuit design, repair, and troubleshooting.
This system allows users to identify resistor values, which directly impact the performance of electronic circuits. In microcontroller-based projects, various components are used, which include sensors, relays, diodes, and resistors. Resistors are used for tasks like voltage division and current limiting for LEDs. So, identifying the correct resistor based on the color code is essential.
How Does a Resistor's Color Code Work?
Resistors' color code is essential for measuring their exact value. The color bands are read from left to right, where the first two or three bands represent significant digits, the next band is a multiplier, and the last band indicates tolerance.
Consider a resistor with color bands: Red, Violet, Orange, and Gold. According to the resistor color code chart, the value of Red (1st digit) is 2, the value of Violet (2nd digit) is 7, Orange is a multiplier, and Gold is a tolerance. So,
Red = 2 (1st digit)
Violet = 7 (2nd digit)
Orange = ×1,000 (Multiplier)
Gold = ±5% (Tolerance)
Resistance = 27 x 1,000 = 27,000 ohms or 27kohm +- 5%.
Resistor Color Code Chart
The resistor color code chart is a standardized reference used to decode the colored bands on resistors, which indicate their resistance value, multiplier, and tolerance.
Color | Digit Value | Multiplier | Tolerance |
Black | 0 | ×1 | – |
Brown | 1 | ×10 | ±1% |
Red | 2 | ×100 | ±2% |
Orange | 3 | ×1,000 | – |
Yellow | 4 | ×10,000 | – |
Green | 5 | ×100,000 | ±0.5% |
Blue | 6 | ×1,000,000 | ±0.25% |
Violet | 7 | ×10,000,000 | ±0.1% |
Gray | 8 | ×100,000,000 | ±0.05% |
White | 9 | ×1,000,000,000 | – |
Gold | – | ×0.1 | ±5% |
Silver | – | ×0.01 | ±10% |
No Color | – | – | ±20% |
How To Read Resistor Color Code?
To identify the correct resistance value, we use the resistor color code. Below are the steps for calculating the resistance.
1. Identify the Number of Color Bands
Firstly, identify the number of color bands on the resistors, whether they are 4-band, 5-band, or 6-band resistors.
2. Determine the Reading Direction
Start reading from the end with the band closest to the edge or from the side with metallic gold/silver (which usually represents tolerance).
3. Resistor Color Code Chart
We use the resistor color code chart to identify the exact value of the band.
4. Apply the Formula
After all the information, to calculate the resistance value with the help of the formula: Resistance = (First Digit) (Second Digit) × Multiplier ± Tolerance
Tips For Reading Resistor Codes
The following are some tips for reading resistor codes:
1. Always use the resistor color code chart, which will help to decode each band’s meaning, whether it's a significant digit, multiplier, or tolerance level.
2. To read the bands, start from the left side, where the colored bands are nearest to the edge. If you see a gold or silver band, that’s the tolerance band, and you should read it last. If you begin from the wrong end, you might get a different resistance value.
3. Identify the resistor representation by using bands, whether it is 4 4-band resistor, 5 5-band resistor, or 6 6-band resistor. Correctly counting the bands ensures you apply the right formula to calculate resistance.
4. Give more attention to identifying the proper color. Use good lighting or a magnifier if needed, particularly when working with small resistors on development boards or densely packed PCBs.
5. Identifying tolerance is always essential for critical applications. Always check the last color band to ensure the resistor meets the required accuracy (e.g., ±1%, ±5%, ±10%).
6. For confirmation about the correct resistance value, use a multimeter.
4 Band Resistors
This type of resistor is most commonly used in general-purpose electronics. It includes four bands: band 1 (1st significant digit), band 2 (2nd significant digit), band 3 (Multiplier - power of 10), and band 4 (Tolerance - accuracy of the resistor). A 4-band resistor is ideal for basic electronics, DIY projects, and circuits using microcontrollers like Arduino, ESP32, or Raspberry Pi.
Red (2), Violet (7), Orange (×1,000), Gold (±5%)
Resistance = 27 × 1,000 = 27,000 ohms (27kΩ) ±5%
5 Band Resistors
This type of band resistor is used in high-precision applications and is often used in sensitive and advanced applications. They have five bands, which include band 1 (1st significant digit), band 2 (2nd significant digit), band 3 (3rd significant digit), band 4 (Multiplier), band 5 (Tolerance). They are used in sensor signal conditioning, analog IC applications and precision measurement systems.
Example:
Brown (1), Green (5), Black (0), Red (×100), Brown (±1%)
Resistance = 150 × 100 = 15,000 ohms (15kΩ) ±1%
6 Band Resistors
This is a precision resistor that has an extra band for temperature coefficient, which indicates how much the resistance changes with temperature. They have five bands, which include band 1 (1st significant digit), band 2 (2nd significant digit), band 3 (3rd significant digit), band 4 (Multiplier), band 5 (Tolerance), band 6 (Temperature coefficient (ppm/°C)).
It is used in aerospace electronics, medical devices, and high-end sensor systems where stability over temperature is critical.
Yellow (4), Violet (7), Black (0), Orange (×1,000), Red (±2%), Brown (100 ppm/°C)
Resistance = 470 × 1,000 = 470,000 ohms (470kΩ) ±2%, Temp Coeff = 100 ppm/°C
Color Code Exceptions
Even if the resistor color code system is widely used but there are certain color code exceptions about which we should be aware.
1. Faded or Discolored Bands
Color band gets faded or changes due to overheating when exposed for a long time. This makes it difficult to accurately determine resistance using the color code. In such cases, a multimeter should be used to verify the actual resistance.
2. Non-Standard Band Patterns
Some resistors follow a non-standard coding system or use special marking formats (e.g., alphanumeric codes instead of colored bands). These are precision resistors with tolerances and may not follow the typical 4, 5, or 6 band format.
