Resistor Color Coding

Fixed resistors are marked in several ways. These are:

1. Color coding
2. Straight numerical  value
3. Certain numerical codes that can be easily translated

Because carbon resistors are small physically, they are color coded to mark their R value in ohms. In memorizing the colors, note that the darkest color, black and brown are the for the lowest numbers, zero and one, through lighter colors to white for nine.

Typical Example on How to Calculate the Resistor Color Code

Reading form left to right, the first band close to the edge gives the first digit in the numerical value of R. the next band marks the second digit. The third band is the decimal multiplier, which gives the number of zeros after the two digits.

Example 1:

The first band is red for 2 and the next band is violet for 7. The red multiplier in the third band means add two zeroes to 27. The result can be illustrated as follows:

Therefore, this R value is 2700Ω with tolerance ±5%.

The resistor tolerance means the amount by which the actual R can be different form the color-coded value. For instance, the alone value 2700Ω resistor with ±5% tolerance can have resistance 5 percent above or below the coded value.

This R, therefore, is between 2565Ω and 2835Ω. the calculations are as follows:

5 percent of 2700 is 0.05 x 2700 = 135

For +5 percent, the value is               2700 + 135=2835Ω

For -5 percent, the value is                2700 – 135 = 2566Ω

Example 2:

Therefore, the R value is 56000Ω or 56KΩ with tolerance ±10%.

Example 3:

The example 3 illustrates that black for the third band means “do not add zeroes to the first two digits”. Since the resistor has orange, orange and black band, the R value is 33Ω with tolerance ±5%.

Example 4:

18 x 1 = 18Ω

Therefore, the R value is 18Ω with tolerance ±10%.

Example 5:

For these values, the third band is gold, indicates a fractional decimal multiplier. When the third band is gold, multiply the first two digits by 0.1. The R value is