Have you ever had troubles reading resistor color codes? Picking a resistor and being able to instantly know its value from the color band code is a very useful skill to anyone interested into electronics.

Resistor code calculator

In this short post you’ll learn how to read resistor values from the color code, and you can practice with our online resistor code calculator. Just choose the color of each band and you’ll get the resistor value!

1 - Why using a band color code?

In resistors resistance value is not written as a number but with different circular color bands in the body of the resistor. Resistors are quite small so using this kind of coding instead of printing a number makes it easier to identify them. Being able to read the value of a resistor is a required skill whether you want to to build an effect pedal kit or any other electronic circuit. Once you get used to the color values, you'll see how easy it becomes!

2 - Band color values

In resistor color coding each color is assigned a value. The following chart gives the conversion between each color and its numeric value: For the tolerance band,
- brown: 1%
- gold: 5%
- silver: 10%

3 - Resistor code format

In a resistor the color code always work the same way: Value bands: depending on the resistor, two or three bands may appear. These color bands are telling you the "base value" of the resistor (ie., "47" in a 47k resistor, 82 in a 8.2k resistor and so on). Number of zeros: this band indicates the number of zeros you have to add to the value obtained with the value bands to get the real value. For example, one possibility for a 47k resistor would be yellow-purple-orange:

Value bands = 47 (yellow and purple)
Zeros Band = 3 (orange)

Tolerance band: this band sets how much the real value can vary from the value you get from the code (check our resistor post to learn more about resistor tolerance and other parameters!).

The tolerance value is determined by the last color band.

• Brown: 1%
• Gold: 5%
• Silver: 10%

For example, in a 100k resistor with a brown tolerance band the real value could swing from 99k (100k - 1%) to 101k (100k + 1%).

Resistor value examples

1 - Carbon film resistors

Most of these resistors have a clear brown packaging with four bands on it, and their name comes from the fact that they use a carbon film inside them to create the desired resistance. Carbon film resistors usually have 4 color bands, with their values distributed according to the E24 series and a 5% tolerance.

• two for the color code
• one for the number of zeros
• one for the tolerance

Let's check an example:

• Color code: 8 2 (grey red)
• Number of zeros: 3 (orange)
• Tolerance: 5% (gold)
• Value: 82kΩ ± 4.1kΩ

1 - Metal film resistors

These resistors usually have a 1% tolerance and a clear blue packaging. The code consists of five bands, and in these resistors a metal film is used instead. Resistance values are distributed according to the E96 series. with the following band distribution:

• three bands for the color code
• one band for the number of zeros
• one band for the tolerance

And now an example:

• Color code: 5 6 0 (green blue black)
• Number of zeros: 4 (yellow)
• Tolerance: 1%
• Value: 5.6MΩ ± 56kΩ

Even if it may seem daunting at first, the best way to learn how to read resistor values is...reading them! If you want a quick reference you can download and print our resistor value cheat sheet.

 

Don't miss the other posts from the resistor series:

• Electronic Tutorials: the Resistor
• The truth behind electronic component values