Complete Guide to Resistor Color Code and Number Code with Calculations

Resistors are fundamental components in electronic circuits, used to limit current and divide voltage. Identifying the resistance value of a resistor is crucial for its proper application. Two common methods for marking resistor values are the colour code system and the number code system.

Discover how to accurately calculate resistor values using colour codes and numbers. Enhance your electronics skills with our comprehensive guide.

Resistor Color Code System

The colour code system is widely used for axial lead resistors. This method uses coloured bands printed on the resistor to indicate its resistance value, tolerance, and sometimes temperature coefficient.

Standard Resistor Color Code Chart

Each colour corresponds to a specific number, multiplier, or tolerance:

Understanding the Bands

Most resistors use 4-band, 5-band, or 6-band systems:

➔ 4-Band Resistor:

• 1st Band: First significant digit.
• 2nd Band: Second significant digit.
• 3rd Band: Multiplier.
• 4th Band: Tolerance.

Example: A resistor with bands Yellow, Violet, read, and Gold:

• Yellow (4), Violet (7): $47$
• Red multiplier ($10^2$): $47\times 100=4,700\mathrm{\Omega }$ or $4.7k\mathrm{\Omega }$
• Gold: ±5% tolerance.

➔ 5-Band Resistor (higher precision):

• 1st Band: First significant digit.
• 2nd Band: Second significant digit.
• 3rd Band: Third significant digit.
• 4th Band: Multiplier.
• 5th Band: Tolerance.

➔ 6-Band Resistor (includes temperature coefficient):
The additional 6th Band represents the temperature coefficient (ppm/°C).

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Resistor Number Code System

For Surface-Mount Device (SMD) resistors, the number code system is used due to space limitations.

➔ 3-Digit Code

• First two digits: Significant digits.
• Third digit: Multiplier (power of 10).

Example:

• 473: $47\times 10^3=47,000\mathrm{\Omega }$ or $47k\mathrm{\Omega }$.

➔ 4-Digit Code

• First three digits: Significant digits.
• Fourth digit: Multiplier.

Example:

• 4702: $470\times 10^2=47,000\mathrm{\Omega }$ or $47k\mathrm{\Omega }$.

➔ R Notation

For low resistances, the letter R replaces the decimal point.

Examples:

• 4R7: $4.7\mathrm{\Omega }$.
• 0R22: $0.22\mathrm{\Omega }$.

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Calculations and Tolerance

Resistance Calculation

The resistance value is calculated by combining the digits and applying the multiplier.

Formula: $R=(SignificantDigits)\times Multiplier$

Tolerance

Tolerance indicates the possible variation in the resistor's value.

Example:

• A $1,000\mathrm{\Omega }$ resistor with ±5% tolerance:
  • Minimum resistance: $1,000\times 0.95=950\mathrm{\Omega }$.
  • Maximum resistance: $1,000\times 1.05=1,050\mathrm{\Omega }$.

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Examples for Practice

➔ 4-Band Resistor: Red, Red, Brown, Gold

• Significant digits: $22$.
• Multiplier: $10^1$ ($\times 10$).
• Resistance: $22\times 10=220\mathrm{\Omega }$.
• Tolerance: ±5%.

➔ SMD Resistor: 102

• Significant digits: $10$.
• Multiplier: $10^2$.
• Resistance: $10\times 100=1,000\mathrm{\Omega }$ or $1k\mathrm{\Omega }$.

➔ 5-Band Resistor: Green, Blue, Black, Red, Brown

• Significant digits: $56$.
• Multiplier: $10^2$.
• Tolerance: ±1%.
• Resistance: $56\times 100=5,600\mathrm{\Omega }$ or $5.6k\mathrm{\Omega }$.

Conclusion

Understanding resistor colour and number codes is essential for electronics design and troubleshooting. With practice, interpreting these codes becomes intuitive. Whether using colour bands or numerical markings, these systems provide an efficient way to identify resistance values, tolerances, and other characteristics.