Resistor Color Code Calculator

How to Use It?

To use the calculator, just choose the color for each band and watch how the actual bands on the resistor illustration change. You will also see the resistance value and its tolerance.

A cool feature of this calculator is that it can be used in reverse; That is, instead of calculating the resistance value based on color bands, you can enter a resistance value and it will tell you what color bands will be on that resistance.

Resistor Color-coding

Resistor color-coding is a way of representing the resistance value of a resistor using colored bands. The colors are assigned to specific values, and the bands are arranged in a specific order. This allows engineers and technicians to quickly and easily identify the resistance of a resistor without having to read the printed value.

The resistance value, tolerance, and wattage rating are typically printed in numbers or letters on the resistor’s body, especially for larger power resistors. For smaller resistors, like 1/4 watt carbon or film types, the print would be too small to read, so the color code was developed in the early 1920s.

The Resistor Color-coding is defined in the international standard IEC 60062:2016.

4-Band Resistor Color Code System

Resistors typically have three to six bands indicating resistance, tolerance, and, in some cases, temperature coefficient of resistance (TCR). Because this calculator supports resistors with four bands, we’ll discuss the 4-Band Resistor Color Code System.

In a 4-band resistor color code system, the first two bands represent the significant digits of the resistance value, the third band represents the multiplier, and the fourth band represents the tolerance.

Here’s a breakdown of each band:

First Band (Significant Digit):

This band represents the first significant digit of the resistance value. Each color is assigned a specific numerical value from 0 to 9. The following table shows the color-code assignments for the significant digits:

Second Band (Significant Digit):

This band represents the second significant digit of the resistance value and follows the same color-code assignments as the first band.

Third Band (Multiplier):

This band indicates the multiplier or the number of zeros to be added to the significant digits. Each color corresponds to a specific power of 10. The following table shows the color-code assignments for the multiplier:

Fourth Band (Tolerance):

This band represents the tolerance, which indicates the maximum allowable deviation from the stated resistance value. It is typically expressed as a percentage. The following table shows the color-code assignments for the tolerance:

Calculating the Resistance Value

To calculate the resistance value, first identify the reading direction by looking for the tolerance band, which is usually gold or silver and has a wider width or gap than the other bands. If a gold or silver band is present, it must be at the right end.

Next, find the corresponding digits for the first two bands. Write them down in order. Then find the corresponding multiplier for the third band and multiply the two digits by this factor to get the resistance value in ohms.

Finally, find the corresponding tolerance for the fourth band. This is a percentage that indicates how much the actual resistance can vary from the nominal value.

Let’s consider an example: a resistor with the color bands: Yellow, Violet, Red, Gold.

The first band is Yellow, representing the digit 4.

The second band is Violet, representing the digit 7.

The third band is Red, representing the multiplier 100Ω.

Combining the first two digits (47) and multiplying by the multiplier (100Ω), we get a resistance value of: 47 x 100 = 4700Ω = 4.7kΩ.

The fourth band is Gold, representing a tolerance of ±5%.

Therefore, the resistor has a resistance value of 4.7kΩ with a tolerance of ±5%.