Let’s learn about **resistors**, which are essential in circuit construction. It is one of the most basic and widely used electronic components. If the resistor has a similar shape to the axial type, you can check the resistance value by reading the color code according to the resistance value.

The **color code** usually has four **colored bands**, with the first three bands representing the resistance value and the last band representing the tolerance. The first band represents the first number and the second band represents the second number.

These two numbers combine to give the default resistance value. The third band represents the multiplication factor, which is multiplied by the base value to give the actual resistance value. The last band represents the tolerance. This indicates how much the actual resistance value may differ from the default value.

## Resistor color code

Resistance values are usually displayed as color-coded bands.

Electronic color codes are codes used to rank specific electrical components, such as the resistance (in ohms) of a resistor.

### How color coding works

Color coding of resistors is an international standard defined in IEC 60062. Resistor color codes shown in the table below include different colors to indicate significant digits, multiplier, tolerance, reliability, and temperature coefficient.

### How to Read Resistor Codes

The 4-band color code is the most common variation. This resistor has two bands for resistance value: a multiplier band and a tolerance band.

For example, consider a resistor made up of four bands: green, blue, red, and gold.

Using the color code chart, green represents 5 and blue represents 6. The third band is the multiplier and the red color represents the multiplier value of 2 (102). Therefore, the value of this resistance is 56·102 = 56·100 = **5600Ω**. The gold band indicates that the resistor has a tolerance of 5%. Therefore, the resistance value lies between 5320 and 5880 Ω (5560 ± 5%). If you leave the tolerance band blank, the result is a three-band resistance. This means that the resistance value remains the same but the tolerance is 20%.

As another example, a resistor with colored bands of red-red-brown-gold indicates a resistance value of **22 (red-red) x 10 (brown) = 220 ohms, with a tolerance of ±5% (gold)**.

If in doubt due to discoloration, measure resistance with an ohmmeter. In some cases, this may be the only way to determine resistance.

## SMD Resistor Code

SMD resistor stands for “Surface Mount Device” and refers to a surface mounted component. This small chip displays the resistance value using a 3- or 4-digit numeric code called an SMD resistance code, which indicates the resistance value.

Typically, a 3-digit numeric code indicates a ±5% tolerance, and a 4-digit numeric code indicates a ±1% tolerance.

### Read 3-digit SMD resistance code

The first and second numbers represent a two-digit number, and the third number represents a multiple of 10. And the “R” designation indicates the decimal point position for resistances less than 10Ω.

Example) 220 : 22 x 1 = 22Ω

103 : 10 x 1000 = 10000 = 10KΩ

915 : 91 x 100000 = 9100000 = 9.1MΩ

4R7: 4.7Ω

R56: 0.56Ω

### Read 4-digit SMD resistance code

The first to third numbers represent a three-digit number, and the fourth number represents a multiple of 10. And the “R” in the first digit indicates the decimal point position in case of resistance less than 100Ω.

Example) 2201: 220 x 10 = 2200 = 2.2kΩ

1000 : 100 x 1 = 100Ω

1004 : 100 x 10000 = 1000000 = 1MΩ

R102: 0.102Ω

25R5: 25.5Ω

### Useful reference site

- https://en.wikipedia.org/wiki/Resistor
- https://www.digikey.com/en/resources/conversion-calculators
- https://www.arrow.com/en/research-and-events/articles/resistor-color-code

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