How to Read Resistor Color Code
Resistors can come in different sizes and shapes allowing for different voltages to go through it. However, unless the size of the resistor is large, the code is rarely written on it because it would require very tiny markings. Therefore, a system was developed to use colors to determine the resistor code. In other words, by using different colors, an average user can determine exactly what the Ohms are for the resistor.
Reading Resistor Code
| Black | 0 |
| Brown | 1 |
| Red | 10 |
| Orange | 100 |
| Yellow | 1000 |
| Green | 10000 |
| Blue | 100000 |
| Gold | 1/10 |
| Silver | 1/100 |
Count the number of color bands on the resistor. For resistors with a tolerance anywhere from 5% to 10%, there will be four bands. For resistors with a tolerance anywhere from 1% to 2%, there will be five bands. For four band resistors, the first two bands are the value digits, the third band is the multiplier and the fourth is the tolerance. For five band resistors, the first three bands are the value digits, the fourth is the multiplier and the fifth is the tolerance.
The 4-band code is used for marking low precision resistors with 5%, 10% and 20% tolerances. Identifying the value will become easy with a little practice, as there are only a few simple rules to remember:
- The first two bands represent the most significant digits of the resistance value. Colors are assigned to all the numbers between 0 and 9, and the color bands basically translate the numbers into a visible code. Black is 0, brown is 1, red is 2 and so on (see the color code table below). So, for example, if a resistor has brown and red as the first two bands, the most significant digits will be 1 and 2 (12).
- The third band indicates the multiplier telling you the power of ten to which the two significant digits must be multiplied (or how many zeros to add), using the same assigned value for each color as in the previous step. For example, if this band is red (2), you will multiply it by 102 = 100 (or add 2 zeros). So, for the resistor we used in the previous example, the value would be: 12 x 100 = 1200Ω (1.2kΩ).
Note: If the multiplier band is gold or silver, the decimal point is moved to the left by one or two places (divided by 10 or 100). - The tolerance band (the deviation from the specified value) is next, usually spaced away from the others, or it’s a little bit wider. A color is assigned to each tolerance: gold is 5%, silver is 10%. 20% resistors have only 3 color bands – the tolerance band is missing. So, for a 560 ohm, 5% resistor the color stripes will be green, blue, brown and gold. Green and blue are the first significant digits (56); brown is the multiplier (101 = 10) and gold is the tolerance (5%). 56 x 10 = 560Ω.
| Brown | 1% |
| Red | 2% |
| Gold | 5% |
| Silver | 10% |
If the 3rd band would be red instead of brown, the multiplier would be (102 = 100) instead of 10 and the resistor value would be 56 x 100 = 5600 ohms = 5.6 k ohms.
If the multiplier band is gold or silver, then the decimal point is moved to the left one or two places (divided by 10 or 100). For example, a resistor with green, blue, silver and gold rings has a value of 56 x 0.01 = 0.56Ω.
The 5-band code
The 5 band code is used for marking high quality, precision resistors with 2%, 1% or lower tolerances. The rules are similar to the previous system; the only difference is the number of digit bands. The first 3 bands will represent the value, the 4th band will be the multiplier and the 5th stripe will give us the tolerance.
Optional band
A few resistors have an additional band – often giving beginners a bit of trouble – indicating either the reliability or the temperature coefficient.
The reliability band specifies the failure rate per 1000 hours (assuming that a full wattage being applied to the resistor). This stripe is found primarily on 4-band resistors made for military applications and seldom used in commercial electronics.
The temperature coefficient is more commonly marked, especially on quality 5-band resistors, as it starts to become an important factor for precision components. For a resistor with temperature coefficient of 200 ppm, for example, a change in temperature of 50°C causes a value change of 1%. The most common values for this band are presented in the color chart above.
See also: Resistors
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