Resistor Color Code Calculator

Resistor Color Code Calculator

Category : code JavaScript

I’ve started to learn JavaScript and my first self-assignment task was to program a resistor color code calculator, wich I always wanted to code. You can check it out here! I also strongly recommend the JavaScript course that I’m taking. It’s inexpensive and you can learn very fast. I’m taking a course with Jonas Schmedtmann for the second time. It’s worthy taking a look here.

Resistor Color Code Calculator

No more runaround. If you are a beginner in electronics or if you are a little rusty this post is for you! Here I’ll explain how the resistor color code works so you can know the resistance value just by seeing the colored strips printed on an axial lead resistor. If you don’t want to memorize the code you can just use my 4-band or 5-band resistor type calculator to find out the resistance value. You’re welcome!!

As said in PRACTICAL ELECTRONICS FOR INVENTORS, “Axial lead resistors, such as carbon composition, carbon film and metal film, use color bands to indicate resistance values. The most common labeling scheme uses four bands: the first band represents the first digit, the second band the second digit, the third band the multiplier (as an exponent of 10), and the fourth band the tolerance (if there is no fourth band, the tolerance is 20%).” . The table 1 shows the meaning of each band relating to its position.

4-band 5-band
1st band 1st significant digit 1st significant digit
2nd band 2nd significant digit 2nd significant digit
3rd band multiplier 3rd significant digit
4th band tolerance multiplier
5th band tolerance

Table 1 – Meaning of resistor bands.

The table 2 indicates the meaning of each color in regard to digit, multiplier and tolerance.

Band Color Digit Multiplier Tolerance
Black 0 x100
Brown 1 x101 ± 1%
Red 2 x102 ± 2%
Orange 3 x103
Yellow 4 x104
Green 5 x105 ± 0.5%
Blue 6 x106 ± 0.25%
Violet 7 x107 ± 0.1%
Gray 8 x108 ± 0.05%
White 9 x109
Gold x10-1 ± 5%
Silver x10-2 ± 10%

Table 2 – Resistor Color Code

For example, we can check the resistance value of the first resistor at the picture above. The first band is brown with value of 1, the second band is black with value of 0, the third band is red with a 100 as multiplier and the fourth band is gold with tolerance of ± 5%. So the resistance is equal to 10 x 100 ± 5% = 1 KΩ ± 5%. In other words, the value is between 950 Ω – 1.05 KΩ. The second example is with the second resistor at the picture above. It’s a 5-band resistor with an extra digit normally used for greater accuracy. The first band is brown with value of 1, the second band is black with value of 0, the third band is also black with value of 0, the fourth band is red with a 100 as multiplier and the fifth band is brown with tolerance of ± 1%. So the resistance is equal to 100 x 100 ± 1% = 10 KΩ ± 1%. In other words, the value is between 9.9 KΩ – 10.1 KΩ.

Note that, in reality, the beige-colored body of a resistor is often an indication that its tolerance is 5%, while a blue-colored body often indicates a tolerance of 1% or 2%. There is also a 6-band resistor that includes a temperature coefficient band but I haven’t implemented it. Just remember to read the resistor from left side to right. Usually the gold or silver bands (for tolerance) are present on the right side.

That is it for today. I hope you enjoyed and learned something new! See you around!! 😄

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