Resistors are common electrical components found in many electronic circuits. They are used to limit or control the flow of electrical current. Resistors have colored bands printed on them that indicate their resistance value in ohms as well as their tolerance. To help identify resistor values, an acronym was created using the first letter of each resistor color band.
Introduction to Resistor Color Codes
The resistor color code is a system used to indicate the values or ratings of resistors. It consists of an alternating series of 3-4 color bands that are printed around the body of axial cylindrical resistors. Each color represents a numerical digit or tolerance value. By reading the color bands in a specified order, the resistance, tolerance and sometimes other parameters of the resistor can be determined.
The most common resistor color code system uses 4 bands to indicate the resistor value and tolerance. From left to right, the 1st and 2nd bands represent the first two significant digits of the resistance value, the 3rd band indicates the decimal multiplier, and the 4th band denotes the tolerance. For example, a resistor with bands of yellow, violet, red, and gold would have a resistance of 47 x 102 = 4.7k ohms with a 5% tolerance.
Sometimes 5-band or 6-band codes are used for more precision. The extra bands indicate the temperature coefficient of the resistor. Resistors with no printed color code are usually measured directly to determine the resistance.
Resistor Color Code Acronym
To help remember the meaning of each colored band in a 4-band resistor, an acronym was devised using the first letter of each color:
Black = 0
Brown = 1
Red = 2
Orange = 3
Yellow = 4
Green = 5
Blue = 6
Violet = 7
Gray = 8
White = 9
The acronym spells out the word “BROYGBVGW” which can be used to remember the numeric meaning of each color band.
Resistor Color Code Table
Here is a table summarizing the resistor color code for 4-band through resistors:
| Band Position | Color | Meaning |
|---|---|---|
| 1st | Black | 0 |
| Brown | 1 | |
| Red | 2 | |
| Orange | 3 | |
| Yellow | 4 | |
| Green | 5 | |
| Blue | 6 | |
| Violet | 7 | |
| Gray | 8 | |
| White | 9 | |
| 2nd | All Colors | 0 to 9 |
| 3rd | Black | 1 ohm |
| Brown | 10 ohms | |
| Red | 100 ohms | |
| Orange | 1,000 ohms | |
| Yellow | 10,000 ohms | |
| Green | 100,000 ohms | |
| Blue | 1,000,000 ohms | |
| Violet | 10,000,000 ohms | |
| Gray | 100,000,000 ohms | |
| White | 1,000,000,000 ohms | |
| Gold | 0.1 ohm | |
| Silver | 0.01 ohm | |
| 4th | None | 20% tolerance |
| Gold | 5% tolerance | |
| Silver | 10% tolerance |
How to Read Resistor Color Bands
Here are the steps to read the color bands on a 4-band through-hole resistor:
- Hold the resistor so you can see the bands clearly. The 1st and 2nd bands will be close together at one end.
- Identify the colored bands and their sequence from left to right.
- The 1st and 2nd bands indicate the first two digits of the resistance value. Match the colors to the numbers 0-9.
- The 3rd band is the multiplier. It tells how many zeros to add to the first two digits. Consult the resistor color code chart.
- Combine the first two digits with the multiplier to calculate the full resistance value in ohms.
- The 4th band indicates the tolerance or precision. Common values are 5% and 10%. Gold = 5%, Silver = 10%.
For example, a resistor with color bands Yellow, Violet, Red, Gold would be:
1st & 2nd bands: Yellow = 4, Violet = 7 –> 47
3rd band: Red = x100 multiplier
4th band: Gold = 5% tolerance
Therefore, the resistor value is 47 x 100 = 4,700 ohms with 5% tolerance.
Tips for Remembering Resistor Color Codes
Here are some tips to help remember resistor color codes:
- Use the “BROYGBVGW” acronym to associate the first letter of each color with its number.
- Memorize the numerical order of the colors since they always appear in the same sequence.
- Practice reading the bands on real resistors to get comfortable identifying the colors.
- Refer to a resistor color code chart until you have it memorized.
- Use online calculators or apps to check your work when decoding resistor bands.
- Quiz yourself by looking at the bands and trying to determine the resistance before checking.
- Focus on memorizing the colors for the tolerance bands (gold, silver) first.
Applications of Resistor Color Codes
Resistor color codes are used in many electronics applications including:
- Circuit design – Engineers use the color codes to select appropriate resistance values when prototyping circuits.
- Circuit assembly – Technicians rely on the color codes to ensure they are installing the correct resistors.
- Circuit testing and troubleshooting – The color bands allow quick identification of resistor values to verify operation.
- Resistor manufacturing – Automated processes print the color bands on resistors to label their specifications.
- Inventory management – Color codes help categorize and identify resistor values for stocking and supply chain.
- Quality control – Inspectors can easily check resistor color codes to confirm they meet requirements.
The resistor color code provides an industry-standard system for marking resistance values that simplifies many workflow processes involving resistors.
Resistor Color Code in Other Electronics
Resistor color codes are also used to label components and wires in other types of electronics:
- Capacitors – Some types of capacitors use colored bands to denote capacitance value and tolerance.
- Inductors – Colored dots or bands help identify inductance value for some inductors.
- Transformers – Dots, bands or tape help mark the various leads and wiring connections.
- Wires and cables – Insulated wires use colored insulation, stripes or prints to denote wire gauge and temperature rating.
- Printed circuit boards – Serigraphic prints and patterns on circuit boards identify components, connections and manufacturing data.
- Electronic assemblies – Internal components are often color-coded to aid manufacturing and repair.
The basic concept of using colors for identification has been extended beyond resistors to many aspects of electronics. It provides a simple, visual system for coding important specifications.
Variations of Resistor Color Codes
While the classic 4-band system is the most widely used, there are some variations of resistor color codes to accommodate different precision and manufacturing requirements:
- 5-band – Adds a 5th band for the temperature coefficient of the resistor.
- 6-band – Includes 5 bands for resistance and tolerance plus a 6th for temperature coefficient.
- 2-band – Used on very small or vintage resistors with only 2 bands for the 1st digits.
- 3-band – Like 4-band but lacks the tolerance band to save space.
- Digital printing – Actual resistance values and specs printed or laser etched on the body.
- Silver content – Higher percentages of silver content in the resistive element are indicated.
Manufacturers may use alternate color coding schemes to provide additional information about performance, meet size constraints, or incorporate updated production processes.
Alternatives to Resistor Color Codes
There are alternatives to using resistor color codes to denote resistance values and specifications:
- Direct value printing – The resistance is printed directly on the resistor rather than using color bands.
- Barcodes and QR codes – Resistors have scannable barcodes or QR codes to look up specs digitally.
- RFID tags – Embedded radio-frequency ID tags contain the resistor data accessible wirelessly.
- On-chip registers – Integrated resistor arrays store specs in on-chip registers accessible digitally.
- Package labeling – Detailed technical info printed or attached to packaging for precision resistors.
- Certification testing – Resistors tested and serialized to certify their properties and tolerances.
Direct marking, digital identification, and rigorous testing provide ways to encode comprehensive resistor specifications that do not rely solely on color bands. However, the simplicity of resistor color codes makes them hard to displace completely.
Conclusion
In summary, resistor color codes provide a simple way to mark resistor values using colored bands. The acronym BROYGBVGW helps remember the meaning of each color band for the resistance value digits and multiplier. While resistor color codes originated for resistors, colored markings are now used in many aspects of electronics. The classic 4-band system remains the most common, but variations exist to accommodate different requirements. Alternatives like direct printing and digital identification offer greater precision but lack the easy visual identification of color coded bands.