#Electronics Color Code Because some components are quite small and hard to stamp with text based numerical values, color codes are used to identify the value of these components. These follow a progression based on prismatic colors, like those a rainbow. Axial lead components are color coded with circumferential bands of color to indicate resistance, capacitance and inductance as well as tolerance.
The component value can be decoded by starting with the band closest to one end of the part, where the first 2 bands are value and the 3rd color is a multiplier and the 4th band being tolerance. There also exists a 5 band standard where the first 3 bands are value and the 4th band is a multiplier and the 5 band is tolerance. The five band notation is more common with components with better than 5% tolerances.
| Color | Value | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | 1 | |
| Brown | 1 | 10 | 1% |
| Red | 2 | 100 | 2% |
| Orange | 3 | 1,000 | 3% |
| Yellow | 4 | 10,000 | 4% |
| Green | 5 | 100,000 | 0.5% |
| Blue | 6 | 1,000,000 | 0.25% |
| Violet | 7 | 10,000,000 | 0.1% |
| Gray | 8 | 100,000,000 | 0.05% |
| White | 9 | 1,000,000,000 | |
| Gold | 5.00% | ||
| Silver | 10.00% | ||
| 20.00% |
Many discrete components will have values that define how they will behave in a circuit. While these values should be close to the described value by the manufacturer, the actual value of a part may deviate a certain amount from the stated value.
The maximum deviation allowed from the specified value is known as the tolerance. It is usually given as a percentage of the stated value though for very small capacitors I have seen tolerance specified in pico farads and for quartz crystals in PPM (parts per million) deviation.
Do not assume that a set of components from the same manufacturer and build lot will have values that are evenly distributed throughout the acceptable range of values. A batch ordered with a 20 percent tolerance will likely include no parts having values within 5% of the desired value. There is a cost associated with devices with less tolerance variations, such as with 1% tolerance parts, so this should always be a part of the design considerations.
There are many cases where the values are not critical and less expensive parts can be used while in other cases, such as resistor/capacitor based timing circuits, where tolerance drift can create behavior outside of what is expected or needed.