Resistor & Other Component Identification


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, grey, 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.

1R0 10R 100R 1K0 10K 100K 1M0 10M
1R2 12R 120R 1K2 12K 120K 1M2 n/a
1R5 15R 150R 1K5 15K 150K 1M5 n/a
1R8 18R 180R 1K8 18K 180K 1M8 n/a
2R2 22R 220R 2K2 22K 220K 2M2 n/a
2R7 27R 270R 2K7 27K 270K 2M7 n/a
3R3 33R 330R 3K3 33K 330K 3M3 n/a
3R9 39R 390R 3K9 39K 390K 3M9 n/a
4R7 47R 470R 4K7 47K 470K 4M7 n/a
5R6 56R 560R 5K6 56K 56OK 5M6 n/a
6R8 68R 680R 6K8 68K 680K 6M8 n/a
8R2 82R 820R 8K2 82K 82OK 8M2 n/a


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.

1R0 10R 100R 1K0 10K 100K 1M0
1R1 11R 110R 1K1 11K 110K n/a
1R2 12R 120R 1K2 12K 120K n/a
1R3 13R 130R 1K3 13K 130K n/a
1R5 15R 150R 1K5 15K 150K n/a
1R6 16R 160R 1K6 16K 160K n/a
1R8 18R 180R 1K8 18K 180K n/a
2R0 20R 200R 2K0 20K 200K n/a
2R2 22R 220R 2K2 22K 220K n/a
2R4 24R 240R 2K4 24K 240K n/a
2R7 27R 270R 2K7 27K 270K n/a
3R0 30R 300R 3K0 30K 300K n/a
3R3 33R 330R 3K3 33K 330K n/a
3R6 36R 360R 3K6 36K 360K n/a
3R9 39R 390R 3K9 39K 390K n/a
4R3 43R 430R 4K3 43K 430K n/a
4R7 47R 470R 4K7 47K 470K n/a
5R1 51R 510R 5K1 51K 510K n/a
5R6 56R 560R 5K6 56K 56OK n/a
6R2 62R 620R 6K2 62K 620K n/a
6R8 68R 680R 6K8 68K 680K n/a
7R5 75R 750R 7K5 75K 750K n/a
8R2 82R 820R 8K2 82K 82OK n/a
9R1 91R 910R 9K1 91K 910K n/a


There are also E48 and E96 tables, which have even more different 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.