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Color Coding of Resistors

The resistance value of film resistors is coded on the resistor body in the form of several coloured rings -- normally four or five depending on the standard series (see subsequent pages). Carbon film resistors are normally coded with four rings. The first three rings (starting from the left) stand for the actual resistance value. The first two rings specify a two digit decimal value, while the third ring constitutes a factor by which the decimal value is multiplied; this factor can be higher or lower than one. Finally, the fourth, somewhat offset ring (to the far right) indicates the tolerance of the resistance value. The graphic below demonstrates how the code works.

color-coding-resistors.jpg

 

The following table specifies the color coding for the resistance value:

color-code-resistor-chart.jpg

For the above resistor, the first two rings (brown and black) indicate a decimal number of 10 and the third ring (orange) indicates a multiplying factor of 103, resulting in a total resistance of

R = 10·103 Ohm = 10000 Ohm = 10 kOhm

The colour coding for the tolerance is shown in the following table:

resistors-code-tolerances.jpg

 

In the case of the resistor illustrated above the ring on the far right is gold; the resistor has a tolerance level of ±5%.

The following interactive animation automatically evaluates the colour coded resistors. To do this, use the mouse to select the different ring colours in the list and compare them with the results from the table above.


 

The metal film resistors are normally coded by five rings, whereby in this case, unlike the four-ring coding, the first three rings specify a three-digit decimal value, while the fourth ring is then the multiplying factor and the fifth ring is the tolerance. The following animation illustrates the principle.

 

Metal film resistors may also have besides the coloured rings for resistance values and tolerance, an additional (sixth) color ring to the right of the tolerance ring; this is somewhat wider than the other rings and specifies the resistor's temperature coefficient.

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