Resistors are small electrical components, used in several electrical and electronic circuits to restrict the flow of current within the circuit and also to regenerate voltage drop in several ways. These are available in different sizes and shapes. Each resistor includes a resistance or resistive value that ranges from ohms to milliohms. So these values can be measured through the color band concept. For each small component, a color code is used to indicate the resistance value instead of printed text. So these standard colors specify the rating, value & tolerance. This article discusses what is a resistor color code and how to read it with examples
What is a Resistor Color Code?
These color bands of the resistor are called resistor color codes. Each resistor has different color bands on it that denote the electrical resistance. This was invented by the RMA (Radio Manufacturers Association) in the year 1920s. The power rating of all the resistors can be marked with color bands that rage up to 1 watt. The color bands on the resistor specified the resistance value, rate of tolerance & sometimes failure rates, or the reliability. The resistor color bands range from 3 to 6 where the first two bands specify the value of resistance & the third band is a multiplier.
Please refer to this link for Resistor MCQs
How to Read Resistor Color Code?
The following chart is used to find out the resistance value of the resistor along with tolerance. The following table helps in specifying the band colors once the values are recognized. An automatic resistor color code calculator can also be used to determine the resistance values very quickly. The resistor color coding formula is “BB ROY of Great Britain has a very good wife” which denotes the alphabets of BBROYGBVGW. This code stands for various colors like the following
- B for Black
- B for Brown
- R for Red
- O for Orange
- Y for Yellow
- G for Green
- B for Blue
- V for Violet
- G for Grey
- W for White
|Band Colors||1s Digit||2nd Digit||3rd Digit||Multiplier||Tolerance||Temperature Coefficient|
|Black||0||0||0||1 Ohm||250 ppm/K|
|Brown||1||1||1||10 Ohm||±1% %||100 ppm/K|
|Red||2||2||2||100 Ohm||±2% %||50 ppm/K|
|Orange||3||3||3||1 k Ohm||15 ppm/K|
|Yellow||4||4||4||10 k Ohm||±0.5%||25 ppm/K|
|Blue||5||5||5||100 k Ohm||±1%||20 ppm/K|
|Green||6||6||6||1 M Ohm||± 0.1%||10 ppm/K|
|Gold||0.1 Ohm||± 5%|
How to Calculate Resistor Color Code?
The four band resistor color code can be used to make fewer precision resistors including tolerances of 5%, 10% & 20%. There are some simple rules to identify the resistor values. For example; in the 4 band resistor, the first two colors denote the most important digits for the value of resistance. Each color band is assigned with numbers from 0 to 9 and generally, these bands will decode different numbers into a noticeable code.
For instance, in a four-color band resistor, the first two color bands are brown & red, then the values will be 1 & 2. The 3rd band specifies the multiplier (power of 10) which means the two significant bits should be multiplied through the same allocated value for every color like in the earlier step ( if the band color is 2 then you need to multiply it by 2 so 10^2 = 100 otherwise add two zeros. So, for the previous example, the resistor value would be 1200Ω or 1.2kΩ.
In the above example, if the multiplier band is silver or gold, the decimal point can be shifted to the left through one otherwise two places
Next, the tolerance value and color are allocated to every tolerance. For gold tolerance, it is ± 5%, and for silver, it is ± 10%.
Tolerance can be defined as the error percentage within the resistance value. So, it is how much we can be expecting for an actual measurement of the resistor. For example, if the tolerance = 5%, then we can expect 5% of change within the resistance value. In the same way, if the tolerance is below 2% within a resistor, then this kind of resistor is called a precision resistor. If the resistor doesn’t have tolerance then we have to take it as ±20%.
The temperature coefficient is the sixth color band of the resistor. So, it can be defined as the change within resistance for each one Kelvin change within the temperature. If the temperature of the resistor changes with 1 Kelvin & the 6th band on the resistor is black color, then there will be the alteration of 250 parts for each million within resistors. So, this band is also set up within the resistors with high accuracy.
In 6 band color resistor, each band denotes like the following.
- 1st color band is the first significant digit
- 2nd color band is the second significant digit
- 3rd Color Band is the third significant digit
- 4th color band is Multiplier with a power of 10
- 5th color band is tolerance
- 6th color band is the temperature coefficient of resistance
The resistance color code calculation for 3, 4, 5 & 6 bands resistors is discussed below.
3 Band Resistor Color Code
The resistor with 3 band color code is shown below. In a three-band resistor color code, the first two bands denote the resistance values and the third band is a 1-multiplier band. Generally, the tolerance for the three-band resistor is ±20% which means no tolerance strip.
In the following three-band resistor, the first color is brown-2, the second color is black-0 and the third color is red (multiplier)
The formula for the three-band resistor color code is – 1st digit. 2nd digit x Multiplier
= 1.0X100 = 1000 ±20%
4 Band Resistor Color Code
The resistor with 4 band color code is shown below. In the four-band resistor color code, the first two bands denote the resistance values, 1-multiplier band & 1-tolerance band.
In the following four-band resistor, the first color is brown-2, the second color is black-0, the third color is red (multiplier)
The formula for the three-band resistor color code is – 1st digit. 2nd digit. 3rd digit x Multiplier
= 1.0.X100 = 1000 ±5%
5 Band Resistor Color Code
The resistor with 5 band color code is shown below. In five band resistor color code, the first three bands denote the resistance values, 1-multiplier band & 1-tolerance band.
In the following five band resistor, the first color is brown-2, the second color is black-0, the third color is orange-3, 4th color is red -2 (multiplier)
The formula for the three-band resistor color code is – 1st digit. 2nd digit. third digit x Multiplier
= 1.0.3 X100 = 10.3 kilo ohm ±5%
6 Band Resistor Color Code
The resistor with 6 band color code is shown below. In six band resistor color code, the first three bands denote the resistance values, 1-multiplier band, 1-tolerance band & 1-temperature coefficient value.
In the following six-band color resistor, the first color is brown-2, the second color is black-0, the third color is orange-3, 4th color is red -2 (multiplier), the fifth is tolerance (gold-± 5%) & the sixth band is brown – temperature coefficient (100 ppm/oc)
The formula for the three-band resistor color code is – 1st digit. 2nd digit. third digit x Multiplier = 1.0.3 X100 = 10.3-kilo ohm ±5% 100 ppm/oc.
Thus, this is all about an overview of resistor color code for 3 bands, 4 bands, 5 bands, and 6 bands. Components like resistors can be coded through different colors to recognize their resistance values, tolerance, etc. The size of the resistor denotes the wattage rating. Generally, for large power resistors, the resistance, wattage rating, and tolerance values are indicated on the resistor with letters or numbers. However, for small resistors, it is printed in small letters so the specifications of resistors can be specified in another way. Here is a question for you, what are the different types of resistors?