Introduction: How to Read a Resistor


In electronic circuits, resistors are defined to be devices that have a designed resistance against the passage of an electrical current. One could think of a resistor like a dam that lets the water through but at a controlled rate. It allows the current through it, but it lowers the voltage. These are used commonly within electrical devices. If someone was to open something like a vacuum cleaner or a microwave, there is a high possibility that they would find resistors within them. The simple circuit above shows a resistor, the jagged line, in a circuit.

With this being said, there are resistors with different resistance strength. There are colored bands around a resistor that allow people to know the resistance of the resistor. Each color represents a certain strength as well as other important information for the resistor. The units used for the resistance is Ω, or ohms.

Step 1: Meaning of Each Band

The first step to reading a resistor is understanding what each band means. The way this instructable will orientate the resistor will be to have the fifth band that seems a little isolated on the right-hand side. This also assumes that this is a 5 band color code resistor. There are also 4 and 6 band color code resistors. This guide will not be explaining how to read the 6 band color coded resistor.

Meaning of Digit Bands

Band 1 is the band that is on the far left. This band represents the most significant digit of the resistor. Band 2 represents the second most significant digit of the resistor. Band 3 represents the third most significant digit of the resistor. After these three bands, Band 4 represents the power of 10 you will multiply the first three bands by. For example:

If the first three bands mean 223 and the fourth band means 10^3, the resistance of the resistor is 223 * 10^3 = 223,000Ω or 223kΩ. The k stands for kilo which means thousand.

On the 4 band color coded resistor, the bands are read the same way except you take away the first band from the 5 band color coded resistor.

Meaning of Tolerance Band

The fifth band represents the tolerance of the resistor. The tolerance is the range that the resistors actual value could be. This is to allow for any errors within the resistors resistance. For example:

If the resistor is a 110kΩ with a ±10% tolerance, the actual resistance could range from 99-121kΩ.