Most color codes follow the numbering scheme below:
The first two bands give the value and the third band tells how many zeros to add. If the third band is gold or silver then the decimal is moved to the left by one or two places, respectively (divide by 10 or 100). A fourth band is often present indicating the tolerance and this band often gives beginners a bit of trouble. Just remember that if there are four bands then a gold or silver band at one end is probably the tolerance. This tolerance band is often spaced away from the others or it may be a bit wider. Also watch for an additional band signifying the reliability if the resistors are military surplus.
|Carbon Composition, 2,700,000 ohms (2.7 meg.),5%|
|Carbon Film, 10,000 ohms (10k), 5%|
|Metal Film, 464 ohms, 1%|
After a while, the resistors become familiar - the colors begin to look like numbers when you read a resistor and groups of colors look like familiar values. When you see a yellow, violet, red resistor you will think 4.7k without thinking about each color. And you probably won't even notice the tolerance band! However, when you start to encounter 5-band 1% resistors all of those familiar faces will be gone. Don't worry, few become friendly with 1% color-coded resistors; most of us have to translate them and then check them with an ohmmeter to make sure we are starting at the right end! Five band resistors are read in the same manner except that the first three bands give the value and the fourth gives the number of zeros. The tolerance band is usually brown which indicates 1% as the chart would suggest. You may also encounter very small color-coded resistors with colored bodies. These little marvels can be very hard to read and a good white bench light is very helpful. Try using a wide spectrum fluorescent bulb or a high intensity incandescent. The sun is the best of all! Those little hand magnifiers with the built-in penlight lamp are also helpful.
Precision resistors often have the numeric value printed on the side along with the tolerance and reliability. Sometimes the value is quite easy to read and even includes an omega (ohms symbol) but usually the number follows a scheme similar to color codes. The first digits signify the value and the last digit denotes the number of zeros. If the value is low, an "R" may be included to signify a decimal point. A 2R25 would be a 2.25 ohm resistor.
Capacitors are occasionally color-coded and the most common types use the same table above but the units are picofarads instead of ohms. Sometimes colored dots appear at various places on the capacitor body if it is not axial and the value can be a bit tricky to read.
|680pF - Nearly impossible to read!|
|220 pF, 10%|
Molded inductors follow the same scheme except the units are usually microhenries. A brown-black-red inductor is most likely a 1000 uH. Sometimes a silver or gold band is used as a decimal point. So a red-gold-violet inductor would be a 2.7 uH. Also expect to see a wide silver or gold band before the first value band and a thin tolerance band at the end.
|1000uH (1millihenry), 2%|
|6.8 uH, 5%|