Resistors colour codes system of determining unknown resistor’s value could be hard to be used. But in this post I published, “How to Read Resistor colour codes” makes things easy and simple.

Resistors which their values are not printed on them use colour codes for their resistance identification. This article on resistor colour codes teaches how to determine the value of such resistors.

###### PROCEDURES OF HOW TO READ RESISTOR COLOUR CODES AND USING THE COLOUR CODES TABLE
1. Don’t start from the Gold or Silver colour.
2. The digit for the first colour on the resistor is gotten from the colour codes table under the first band column of that colour. E.g. if the first colour on the resistor is Orange, we write “3”
3. The digit for the second colour on the resistor is the number of zeros under the second band of that colour if the colour is not the same as the first band colour. E.g. if the second colour on the resistor is Yellow, we write 0000 after the first digit of the first band
4. If both the 1st and 2nd band colours are the same, the first digit is written for both of them i.e. in two places. For example if 1st and 2nd band colours of the resistor are green, we will write “55” for the first and second band digits.
5. The third band colour is the multiplier of the first two band digits. For fast calculations, just take the number of zeros under second band of the third colour and write them after the 1st and 2nd digits. For example if the 3rd colour band of the resistor is red, we will write 00 after the digits gotten from the 1st and 2nd band colours. If the third band colour is Gold, we multiply the 1st and 2nd digit by 0.1 or 0.01 if the band is Silver.
6. The final value is the resistance in Ohms (Ω). Divide the value by 1000 if it is more than 3 digits for your answer in Kilo Ohms (KΩ)
7. The fourth band colour is the tolerance.

###### Example 1

A resistor below has BROWN colour first, BLACK second, YELLOW third, and SILVER fourth, what is its value?

We then use the logic

1. On the resistor colour code table under the column FIRST BAND row of BROWN = 1, we then write or note 1 down.
2. Then black is the second colour we then look on the column SECOND BAND row of BLACK = 0, we then write 0 after the 1, we will have two digits now i.e. “10”
3. Then the third colour which is YELLOW, we then look on the column THIRD BAND (the multiplier) = X104 (the “X” stands for the digits from the first and second band i.e. “10”). Therefore we have 10 times the multiples of 10 in 4 places 10(10×10×10×10)

= 10(10,000)

=100,000Ω let’s convert it into Kilo Ohms (KΩ) by dividing it by 1000

=100KΩ (100 Kilo Ohms)

Note that the value of the third colour on a resistor is just the number of zeros under the SECOND BAND of the third colour of the resistor. As in this case YELLOW under second band has 4 zeros (0000).

The shortcut of this method as stated earlier is – the first and the second band colours’ digits are written followed by the zeros of the third colour under its second band, then divide by 1000 (if the final figure is up to a thousand i.e. (four digits) for your answer in KΩ.

In the case of the resistor above,

1. 1st digit (Brown under first band) is 1,
2. 2nd digit (Black under second band) is 0, we then write “10”
3. 3rd values (Yellow under second band) is 0000

Finally we have 100000Ω. Dividing it by 1000, we obtain 100KΩ

###### Example 2

What is the value of the Resistor below (BROWN, BLACK, BROWN, and SILVER)

1. The 1st digit (brown under first band) is 1,
2. 2nd digit (black under second band) is 0, we now write “10”
3. The 3rd digit (brown under second band) is 0.

Finally, we now have 100Ω which its value.

If the third band colour of the above resistor was red; we would write 10 and followed by 00 (red under second band) and our result would be 1000Ω which is equal to 1K Ohms

###### Example 3

What is the resistance of a resistor with these colour codes RED, RED, ORANGE, and SILVER

1. The 1st and 2nd band colours of the resistor above are the same (RED, RED). Therefore, we will write the digit of Red under first band in two places for them. The digit of Red under first band is 2, therefore we will write the 2 in two places i.e. 22.
2. Orange under second band (the zeros) is 000.

Finally we have 22000Ω =22KΩ (divided by 1000)