The Book of Threes
resistor

resistor

* If a resistor has 5 color bands, write the corresponding number of the 3rd band to the right of the 2nd before you multiply by the corresponding number of the multiplier band. If you only have 4 color bands that include a tolerance band, ignore this column and go straight to the multiplier.
 
The tolerance band is usually gold or silver, but some may have none. Because resistors are not the exact value as indicated by the color bands, manufactures have included a tolorance color band to indicate the accuracy of the resistor. Gold band indicates the resistor is within 5% of what is indicated. Silver = 10% and None = 20%. Others are shown in the chart below. The 1K ohm resistor in the example (left), may have an actual measurement any where from 950 ohms to 1050 ohms.

If a resistor does not have a tolerance band, start from the band closest to a lead. This will be the 1st band. If you are unable to read the color bands, then you'll have to use your multimeter. Be sure to zero it out first!

 Resistor Color Codes
Band Color 1st Band # 2nd Band # *3rd Band # Multiplier x  Tolerances  ± %
Black 0 0 0 1  
Brown 1 1 1 10     ± 1%
Red 2 2 2 100     ± 2 %
Orange 3 3 3 1000  
Yellow 4 4 4 10,000  
Green 5 5 5 100,000     ± 0.5 %
Blue 6 6 6 1,000,000     ± 0.25 %
Violet 7 7 7 10,000,000     ± 0.10 %
Grey 8 8 8 100,000,000     ± 0.05 %
White 9 9 9 1,000,000,000  
Gold 0.1     ± 5 %
Silver 0.01     ± 10 %
None     ± 20 %

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Three is the Magic Number

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