|Resistor Color Code Decoding|
Resistors are marked with colored bands to indicate their value. Translating these color bands to numbers is easy, as long as you orient the resistor and read it in the proper order. Generally, there are only four bands. However, there can be as many as six bands.
The colored squares and resistor image are interactive. You can click on the appropriate colored squares and the bands on the resistor will change accordingly. The value and tolerance will also be listed. Note that it is possible to create a color combination for a resistor that doesn't exist. That is why the nearest standard resistor is listed at the bottom of the resistor image.
|Three/Four Band Resistors|
Reading four band resistors is usually pretty straight forward. The color bands are usually grouped to one side of the resistor. So to read the resistor, orient the resistor such that the side with the color band grouping is on the left.
The colors are then read from left to right. The first two color bands define to a two digit number and the third color band defines a multiplier. For example, if the first three colors were, from left to right, red | violet | orange. The colors would translate to 2 | 7 | x1000, or 27,000 Ohms.
The fourth color band indicates the tolerance. The tolerance is a measure of the accuracy of the marked resistance value. For example, if the the fourth band was gold . Gold indicates a 5% tolerance. This means that the actual resistor value will be between 25,650 Ohms and 28,350 Ohms (27,000 +/- 5%).
For four band resistors, the most common resistors are of the 5% and 10% tolerance variety. While 20% resistors (3 Band) resistors still exist, they are not very common.
|Five/Six Band Resistors|
Reading five band resistors should also be relatively easy. However, six band resistors may be a little more difficult. As with the four band resistors, the colors are generally grouped to one side. There are some that place a wide gap between the fourth and fifth color bands so that a colored band exists on the far right and far left. In this case, orient the resistor so that the stand alone color band is on the right, and all other color bands are on the left. Then convert the first three color bands to a three digit number and the fourth color band would be the multiplier.
For example, if the first four colors were, from left to right, red | orange | violet | orange, for the first four color bands. The colors would translate to 2 | 3 | 7 | x1000, or 237,000 Ohms.
The fifth color band indicates the tolerance. The tolerance is a measure of the accuracy of the marked resistance value. For example, if the the fourth band was red . Red indicates a 2% tolerance. This means that the actual resistor value will be between 232,260 Ohms and 241,740 Ohms (237,000 ± 2%).
For five band resistors, the most common resistors are of the 1% and 2% tolerance variety.
|Standard Resistors, 1%, 5%, and 10%|
Standard base resistor values are given in the following tables for the most commonly used tolerances (1%, 5%, 10%), along with typically available resistance ranges. To see values other than the base, use the range selector in the upper right of each table.
Standard resistor values are calculated using the simple formula on the left. The results is then round to the proper number of significant figures (3 for 1% and 2%, 2 for 5% and 10%). The Tolerance Series number indicates how many resistor values are in each decade. For example, 1% resistors have 96 values in each decade. Whereas, 5% resistors only has 24 resistor values in each decade. If the resistor value you require is critical, the 1% resistor range would provide you with a closer value than the 5% range. If you need something more accurate and stable, there are 0.5%, 0.25%, 0.1%, and 0.05% resistors available. However, they may be a little more difficult to find and more expensive.