Guide to the 100 Ohm Resistor Color Code
The 100 Ohm resistor is one of the most common resistors in electronics. Its popularity makes it perfect for learning the resistor color code. It’s useful to be able to readily recognize them in projects, along with other common resistors.
The 100 Ohm resistor color code allows us to quickly identify the resistance value and tolerance of a 100 ohm resistor.
In this article, we’ll cover how to read 4 band, 5 band, and 6 band 100 Ohm resistors.
100 Ohm Resistor Color Bands
It’s important to realize that not all four bands correspond to the amount of resistance in Ohms. The first three bands tell us that the resistor’s nominal value is 100 Ohms, and the 4th band gives us the tolerance of the resistor.
All resistors have a tolerance, which means that the value is unlikely to be exactly 100 Ohms. Higher quality resistors have better tolerances.
Helpful Tips for Using Resistor Color Codes:
1) Identify the last band first. It should be separated from the other bands by a small gap. This band is usually gold or silver, so it is typically the easiest to identify. This band gives us the tolerance of the resistor.
2) After identifying the 4th band, look at the bands on the opposite side of the resistor. The first two bands give us a base value, which needs to be multiplied by the multiplier to identify the full resistance value.
3) The third band is the multiplier. Multiply the value designated by the first two bands with the multiplier to find the full value of the resistor.
This process is covered in greater detail below.
100 Ohm Resistor Color Chart
|4||Tolerance||Gold (or silver)||± 5% (± 10% for silver)|
100 ± 5% Ω
How To Read the 100 Ohm Resistor Color Code
Resistor color codes always have digits, followed by a multiplier and a tolerance value. Six band resistors also add a temperature coefficient.
It’s easiest to learn four band resistors first. Once you learn the four band system, it is very easy to understand five and six band resistor color coding.
The Four Band 100 Ohm Resistor
Each band on the resistor has a specific role:
Band One – 1st Digit: This is the first digit of the resistance value. The first band is brown, which corresponds to the value 1.
Band Two – 2nd Digit: The second digit of the resistance value. This band is black, which corresponds to the value 0. This is added to the right of the first digit (from band one).
Therefore the digits from band one and band two are: 10.
Band Three – Multiplier: Takes the digits and multiplies them by a value given by this band. The actual multiplier is 10n, where n is the value of the band color. In this case, the third band is brown which corresponds to the number 1. Therefore the multiplier is 101 = 10.
So the total value of the resistance given by the colors is 10 (from digits) x 101 (from multiplier) Ω = 100Ω.
Band Four – Tolerance: Gives the value of the tolerance for the resistor. The most common values are 5% (designated by a gold band), and 10% (designated by a silver band). This example uses a gold band, giving us a tolerance of 5%.
The total resistance is therefore: 100Ω ± 5% Ω.
This means that the actual resistance value could be anywhere from 95 Ω to 105 Ω.
If the fourth band is silver, this means that the tolerance is 10% and the total resistance is 100Ω ± 10% Ω. The actual resistance should be between 90 Ω and 100 Ω.
You can use a multimeter to find out the actual resistance, but note that it will also vary slightly with temperature. In 6 band resistors, the temperature dependence is given by the last band (more on this below).
Multimeters are a great way to check any resistors you aren’t sure of or to determine the actual resistance of a specific resistor. Just be sure to follow practical safety guidelines.
4-Band vs. 5-Band vs. 6-Band 100 Ohm Resistor Color Code
You will probably encounter 5 band or even 6 band resistors.
It is very easy to read 5 or 6 band resistors if you already know how to use four band resistor color coding.
5 Band 10K Resistor Color Code
For 100 Ohm resistors with five bands, the first three bands will be brown, black, and black (indicating 100) and the fourth band will be black indicating a multiplier of x1.
|5||Tolerance||Gold (or silver)||± 5% (or ± 10%)|
100 ± 5% Ω
4-Band vs. 5-Band vs. 6-Band 100 Resistor Color Code Table
|4-Band Resistor||5-Band Resistor||6-Band Resistor|
|1st band||1st digit of resistance value||1st digit of resistance value||1st digit of resistance value|
|2nd band||2nd digit of resistance value||2nd digit of resistance value||2nd digit of resistance value|
|3rd band||Multiplier (x 10, 100, etc)||3rd digit of resistance value||3rd digit of resistance value|
|4th band||Tolerance (± %)||Multiplier (x 10, 100, etc)||Multiplier (x 10, 100, etc)|
|5th band||N/A||Tolerance (± %)||Tolerance (± %)|
|6th band||N/A||N/A||Temperature Coefficient R(T)|
4 Band vs. 5 Band 100 Ohm Resistor
Four band resistors have two bands for the value, one for the multiplier, and one for the tolerance.
Five band resistors add an extra band for the value.
Therefore five band resistors have three bands for the value, one for the multiplier, and one for the tolerance. The process of analyzing the resistor is the same; start with the 5th band, looking for a small gap between the fourth and fifth band. This will be the tolerance. Then go back to the first four bands to calculate the resistance value.
For a 100 resistor with five bands, we should see an order of brown (1), black (0), black (0), black(x1), gold or silver (± 5% or 10%).
6 Band 100 Ohm Resistor
|5||Tolerance||Gold (or silver)||± 5%|
|6||Temp. Coefficient||Any||See Chart Below|
100 ± 5% Ω
Six band resistors are exactly like five band resistors except they have an extra band to indicate the temperature coefficient, i.e. how much the resistance will change with temperature.
In this case, the last two bands (i.e. the fifth and sixth bands) should be closely spaced, with a gap between the fourth and fifth bands.