If you work with electronics, chances are you will at some point have to read resistors’ color codes for your circuits to, for instance, drop the voltage to not burn an LED light. While reading resistors might involve a little bit of math, it allows you to determine the resistance of the resistor without using an ohmmeter, which you will learn how to read in this article.
Resistors are used to decrease the electric current of a circuit. The electric current will be restricted depending on how much resistance value resistors have. If resistors have a high resistance value, the electric current will decrease in a large amount. On the other hand, if resistors have a low resistance value, the electric current will decrease in a small amount.
Resistors have colors codes that determine not only the resistance value, but also their tolerance, and in some cases, their temperature coefficient and failure rate. Color codes were defined by the international standard IEC 60062, which describes the marking codes for resistors and capacitors.
Since resistors can come in different sizes, shapes, and resistance values, using color codes allows determining easily their resistance value. In this article, we are going to look at the resistor color code chart, how to read the resistance value based on how many color bands resistors have, as well as explain other concepts such the tolerance and failure rate.
Table of Contents
Resistor Color Code Chart
The chart below shows the color codes used to determine resistors’ resistance values. Let’s take a look at it to get familiarized with the color values going deep into explaining how to read determine resistance values
One important detail to notice in the chart above is the colors gold and silver are only used as multipliers and also to determine the tolerance rate of the resistors.
Read Three-Band Resistor
Let’s look at the following diagram to get an idea of how to read a three-band resistor.
In a three-band resistor, the first two bands represent the resistance value digits and the third band represents the multiplier. Three-band resistors don’t have a tolerance band.
In the example above, the three bands are red, red, and black. If we look at the color code chart, that means we have the digits 2 and 2 for the first two bands and the multiplier 1 for the third band. Therefore, the value of the resistor is 22 x 1 = 22Ω.
Since three-band resistors don’t have a color band describing the tolerance rate, it is inferred the resistor’s tolerance is 20%.
Read Four-Band Resistor
Four-band resistors are the most common type of resistors. They are read almost the same you read a three-band resistor, with the addition of reading a fourth-band describing the tolerance rate of the resistor. Therefore, four-band resistors have the first two bands representing the resistance value digits and the third band representing the multiplier, and a fourth band determining the tolerance rate.
If we take a look at the previous example, we have the following colors: red, red, brown, and gold. This means we have digits 2 and 2, with a multiplier of 10 and a tolerance of 5%. Hence, the resistance value of that resistor is 22 x 10 = 220Ω ±5%.
Read Five-Band Resistor
Five-band resistors provide a more detailed resistance value than three-band and four-band resistors. In a five-band resistor, the first three bands represent the resistance value digits, the fourth band stands for the multiplier, and the fifth band is used to determine the tolerance rate.
If we take a look at the previous example, we have the following colors: brown, black, black, black, and brown. This means we have digits 1, 0, and 0, with a multiplier of 1 and a tolerance of 1%. Hence, the resistance value of that resistor is 100 x 1 = 1000Ω ±1%.
Read Six-Band Resistor
Six-band resistors are read almost the same way five-band resistors are read with the addition of reading the temperature coefficient of resistance (TCR). Hence, in a six-band resistor, the first three bands represent the resistance value digits, the fourth band stands for the multiplier, the fifth band is used to determine the tolerance rate, and the sixth band determines the temperature coefficient.
If we take a look at the previous example, we have the following colors: brown, black, black, black, brown, and red. This means we have digits 1, 0, and 0, with a multiplier of 1, a tolerance of 1%, and a TCR of 50 ppm/K. Hence, the resistance value of that resistor is 100 x 1 = 1000Ω ±1% 50 ppm/K.
What is the Resistor Tolerance?
The tolerance in a resistor is the difference of the listed value of the resistor. In other words, it is a percentage of error of a resistor’s resistance value. Hence, that means if we have a four-band resistor of 220Ω with a tolerance rate of ±5%, the actual resistance value of the resistor could range between 242 Ω and 198 Ω.
To calculate the range of the actual resistance value based on tolerance rate, multiply the listed resistor’s resistance value times the tolerance rate percentage. Then, use the result to subtract or add to the listed value of the resistor.
Value of Resistor x Tolerance Rate = Difference
Value of Resistor – Difference = Lowest Possible Resistor Value
Value of Resistor + Difference = Highest Possible Resistor Value
Gold and silver are typically used to denote the tolerance rate of four-band resistors.
Three-band resistors don’t have a band denoting the tolerance rate. Hence, it is inferred for three-band resistors to have a ±20%.
What is the Temperature Coefficient of a Resistor?
After looking at how to read all of the different kinds of resistors based on the total of band colors, the six-band resistors use one color band to determine the temperature coefficient of a resistor (TCR). However, do you understand what does the temperature coefficient means?
The temperature coefficient of a resistor (TCR) determines the total resistance value change as the resistor temperature changes. The temperature coefficient is measured in ppm/°C (parts per million per degree Centigrade). However, they can also be expressed in ppm/°K (parts per million per degree Kelvin).
The temperature coefficient is typically found in high precision resistors which have
Why not using numbers instead of a color code?
Printing the resistance value in the resistor might sound like a good idea. However, resistors can come in different sizes, some of them being too small. Hence, the size of the letters printed in the resistors would be hard to read. Also, it is possible there wouldn’t be enough space to provide important information such as the tolerance rate, the failure rate, and even the resistance value whenever the value is high.
Drawbacks of Color Code
While having a color code is a smart and easy way to denote the resistance value of resistors, there are some drawbacks to using colors. For example, whenever resistors exceed their temperature levels and get burned, it could be hard to determine the colors of the bands. Also, due to the nature of being color-coded, it would prevent blind people from reading the resistors’ values
How to Remember Resistors’ Color Codes
Using mnemonics
Remember the value of each color code can be complex. A common way to memorize the color code chart is to come up with mnemonics, which include the first letter of each color in a sentence.
The first step is to order the values of each color code and determine the first letter of each color.
0 = Black
1 = Brown
2 = Red
3 = Orange
4 = Yellow
5 = Green
6 = Blue
7 = Violet
8 = Gray
9 = White
Then, come up with an easy-to-remember sentence that includes a word per color that starts with the first letter of the color.
Some of the most common mnemonics to memorize resistor color codes are:
- Bye Bye Rosie Off You Go Bristol Via Great Western
- Bye Bye Rosie Off You Go to Become a Very Good Wife
Download the Color Code Chart
For those who will still find it hard to remember the resistors’ color codes using mnemonics, it is recommended to download or print the color code chart and save it in their electronics toolbox to easily refer to it whenever is necessary.
Download the Resistor Color Code Chart.
Step by Step: How to Read a Resistor with a Multimeter
Turn on the Multimeter
In case you haven’t turned on the multimeter, make sure to turn it on.
Set Multimeter on Ohmmeter Mode
Multimeters can help us measure the voltage, current, and resistance. Make sure to set it in ohmmeter or to measure resistance
Place Positive and Negative Probes On Resistor
Locate the resistor in the circuit. Then, take the positive and negative probes and place each probe on one end of the resistor.
Adjust Ohmmeter Range
Adjust the ohmmeter range if necessary. For instance, this multimeter has different ranges to display the resistance value such as in the 200, 2k, 20k, 200k, 2M, and 20M.
Get the Resistor Value
Finally, you should see the value of the resistor. Since I had set it in the range of 2k and I’m measuring a 220Ω resistor, it will show as 0.220Ωk
