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Resistor Color Code Bands
& Other Component Identification

Resistor Color Code Identification

While these codes are most often associated with resistors, then can also apply to capacitors and other components.

The standard color coding method for resistors uses a different color to represent each number 0 to 9: black, brown, red, orange, yellow, green, blue, purple, gray, white. On a 4 band resistor, the first two bands represent the significant digits. On a 5 and 6 band, the first three bands are the significant digits. The next band represents the multiplier or "decade". As in the above 4 band example, the first two bands are red and purple, representing 2 and 7. The third band is orange, representing 3 meaning 10³ or 1000. This gives a value of 27 * 1000, or 27000 Ohms. The gold and silver decade bands divide by a power of 10, allowing for values below 10 Ohms. The 5 and 6 band resistors work exactly the same as the 4 band resistor. They just add one more significant digit. The band after the decade is the tolerance. This tells how accurate the resistance compared to its specification. The 4 band resistor has a gold tolerance, or 5%, meaning that the true value of the resistor could be 5% more or less than 27000 Ohms, allowing values between 25650 to 28350 Ohms. The last band on a 6 band resistor is the temperature coefficient of the resistor, measured in PPM/C or parts per million per degree Centigrade. Brown (100 PPM/C) are the most popular, and will work for most reasonable temperature conditions. The others are specially designed for temperature critical applications.

Alpha-Numeric Code Identification

With the sizes of resistors and other components shrinking or changing in shape, it is getting difficult to fit all of the color bands on a resistor. Therefore, a simpler alphanumeric coding system is used. This method uses three numbers, sometimes followed by a single letter. The numbers represent the same as the first three bands on a 4 band resistor. On the above SIL network, the 4 and 7 are the significant digits and the 3 is the decade, giving 47 x 1000 or 47000 Ohms. The letter after the numbers is the tolerance. The different representations are: M=±20%, K=±10%, J=±5%, G=±2%, F=±1%.

Naming Convention

To simplify the writing of large resistor values, the abbreviations K and M are used for one thousand and one million. To keep the convention standard, R is used to represent 0. Because of problems in seeing the decimal point in some printed texts, the 3 letters: K M or R are used in place of the decimal point. Thus, a 2,700 Ohm resistor is written 2K7 and a 6.8 Ohm resistor is written 6R8.

The E12 Range

These identify a range of resistors that are know as "preferred values". In the E12 range there are 12 "preferred" or "basic" resistor values, and all of the others are simply decades of these values:

1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8 and 8.2

The table below lists every resistor value of the E12 range of preferred values. You will notice that there are 12 rows containing the basic resistor values, and the columns list the decade values thereof. This range most commonly covers standard carbon film resistors, which are not readily available in values above 10 Megohms - 10M (10 Million Ohms)

The E24 Range

The E24 range of preferred values includes all of the E12 values, plus a further 12 to enable the selection of more precise resistances. In the E24 range the preferred values are:

1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2 and 9.1

The table below lists every resistor value of the E24 range of preferred values. You will notice that there are 24 rows containing the basic resistor values and the columns to the right list the decade values thereof. This range most commonly covers metal film resistors which are not readily available in values above 1 Megohm - 1M0.

There are also E48 and E96 tables, which have even more values. Resistors in these groups are less common and tend to have a better tolerance rating.

The table below shows the color codes for the E12 and E24 preferred values. Notice how the first two colors in each row are the same, and the last color in each column is the same. Each column is a decade, and each row in that column is a different one of the E24 values.