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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=ą20%, K=ą10%, J=ą5%, G=ą2%, F=ą1%.

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.

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