Fund. EE Lab I and II
January 2012
Resistors and The Color Code
There are basically two types of fixed-value resistors: general purpose and precision.
Resistors with tolerances of + 5% or greater have four (4) color bands and are referred to as
general purpose resistors. Resistors with tolerances of + 2% or less are classified as precision
resistors and have five (5) color bands. A typical carbon-composition resistor is a general
purpose resistor and is a cylindrical shaped device with two terminals. They have resistance
values ranging from one ohm () up to 20 megohm (M) and power dissipation ratings up to 2
watts (W). The color code indicates both the nominal resistance of the resistor and its precision.
This web site, www.ee.upenn.edu/rca/calcjs.html, at the University of Pennsylvania,
Philadelphia, has a nifty resistor color code calculator.
General Purpose Resistor Color Code – Four Bands
When you pick up a resistor look for a gold or silver band near one end; hold this end in your
right hand. To determine the resistance value refer to Table 1 and note the following:
- the first (left most) band can never be black
- the color of the first band indicates the first digit of the two digit number
- the second band indicates the second digit of the number
- the third indicates the number of zeros to the right of the number
- the fourth band indicates the tolerance or deviation from the specified resistance, which is in
percent and is greater than or equal to 5%.
Table 1. Resistor Color Code.
Digit Color
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Gray
White
Digit Value
0
1
2
3
4
5
6
7
8
9
Tolerance
Color
No band
Silver
Gold
Value
+ 20%
+ 10%
+ 5%
Red
Brown
Green
Blue
+ 2%
+ 1%
+ 0.5%
+ 0.25%
Example. A 5.6 k resistor with 5% tolerance has these color bands (from left to right):
green, blue, red, gold. Green and blue represent 56 and red represents 2 zeros, thus 5600 ohms.
The gold band means the resistor has a 5% tolerance; thus a resistor with this code can lie
between 5600 – 5%(5600) and 5600 + 5%(5600), or 5600 – 280 and 5600 + 280, or between
5320 and 5880 ohms.
Table 2 lists the standard nominal values for 5 % tolerance resistors. For example, the table
indicates that a 180 k resistor is available but not a 170 k resistor; nor is a 140  or a 45 k
resistor available.
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Table 2. Standard Nominal Values For 5%-Tolerance Resistors.
10
11
12
13
15
16
18
20
22
24
27
30
33
36
39
43
47
51
56
62
68
75
82
91
Precision Resistor Color Code – Five Bands
To determine the resistance value note the following:
- the first (left most) band can never be black
- the color of the first band is the first digit of the three digit number
- the second band indicates the second digit of the number
- the third band indicates the third and final digit of the number
- the fourth band indicates the number of zeros to the right of the number
- the fifth and final band indicates the tolerance of the precision resistor, which is always less than
or equal to + 2%. Such resistor are obviously more expensive than general purpose resistors.
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