Electronics Components: Standard Resistor Values - dummies

Electronics Components: Standard Resistor Values

By Doug Lowe

Most resistors used in electronics have four stripes of color. The first three stripes indicate the resistance value, and the fourth stripe indicates the tolerance. Some resistors have five stripes of color, with four representing the resistance value and the last one the tolerance.

In theory, there are 100 different combinations of colors for the first two bands, covering the range of values from 00 through 99. However, in practice there are only a few color combinations that are commonly encountered. These color combinations represent standardized values that allow manufacturers to produce resistors that will be useful in a wide variety of applications.

For example, take the value 47, represented by the color code yellow-violet. 47 happens to be one of the preferred resistor numbers, so you can easily obtain resistors of 4.7, 47, 470, 4.7K, 47K, 470K, and 4.7M.

But 45 is not one of the preferred values. Thus you won’t find 45 or 450 resistors.

Although there are several different systems for standardizing preferred resistor values, the most common system uses 12 different standard values:

First Two Colors Standard Value
Brown – black 10
Brown – red 12
Brown – green 15
Brown – gray 18
Red – red 22
Red – Violet 27
Orange – Orange 33
Orange – white 39
Yellow – violet 47
Green – blue 56
Blue – gray 68
Gray – red 82

These values are standardized values that are designed to provide a wide range of resistance values. Although not exact, each value is approximately 1.2 times larger than the previous value.