# 2. Resistor color code¶

The resistor color code is used to express the value of a resistor in ohms (Ω) and its tolerance, through various colored bands printed on the body of the resistor, which can be seen from any position.

Resistor notation is similar to scientific notation, with a two-digit mantissa and a one-digit exponent.

The following document has exercises to translate all the color codes of the commercial E6 series resistors. Half of the exercises consist of translating color bands into ohms, and the other half consist of translating resistor ohms into color bands. In all the exercises, the tolerance of 5% has been used as it is the most common.

## Color code table¶

International system prefixes:

- µ = micro = 0.000 001
- m = milli = 0.001
- k = kilo = 1,000
- M = Mega = 1,000,000

## Translate colors to numeric value¶

To translate color code to numerical value we will follow the following steps:

Place the resistor in the correct position so that the tolerance color band is on the right.

Most of the time the resistance tolerance is 5% and the band is gold in color, easily distinguishable.

The resistance would stay with the bands

Yellow Violet Orange Gold

Translate the first two color bands to numbers. In the case of the example resistor the colors are yellow and violet.

Yellow = 4

Violet = 7

So the first number is 47

Translate the third color band to a multiplier

Orange band = 3 zeros = multiplier x 1000

Multiply the first number by the multiplier to calculate the final value.

47 x 1000 = 47000 Ohms

Use suffixes to simplify very large values.

47000 Ohms = 47k Ohms

## Special cases¶

When the second band is a zero, you have to take into account that it is added to the zeros of the multiplier.

For example a resistor with the following colors.

Brown Black Red Gold

It is translated as 10 with a multiplier of 100 which turns out to be 1000 Ohms or 1k Ohm.

When the multiplier is Gold, instead of multiplying it must be divided by 10.

For example a resistor with the following colors.

Green Blue Gold Gold

It is translated as 56 with multiplier 0.1 which turns out to be 5.6 Ohms.

## Translate numeric value to colors¶

To translate a resistance value to colored bands we will follow the following steps.

Translate the resistance value to ohms without any prefix. For example for a resistor of 3.9k Ohms

3.9k Ohms = 3900 Ohms

Find the first two color bands from the resistor value. For example for a resistance of 3900 Ohms

3 = Orange

9 = White

Calculate the multiplier to add the missing zeros. In the case of the resistance of 3900 Ohms.

Multiplier = 100 = Red color (2 zeros)

Add the tolerance band of Gold color.

Orange White Red Gold

## Special cases¶

When the second band is a zero, it must be taken into account that it is subtracted from the zeros of the multiplier.

For example a resistor with the value of 100 Ohms.

Brown Black = 10

Needs a Brown x 10 multiplier

The result is

Brown Black Brown Gold

## Quizzes¶

Test-type quizzes to calculate the value of the resistors from the color code or to calculate the colors from the value of the resistor.