What Is Code 128 Check Digit Calculator? 2 Most Useful Tools

Mar 14, 2023 - Views: 148

Rating: 5.0 - 50Votes

If you are working in the supply chain, you must have heard about Code 128. But do you know exactly about code 128 check digit calculator and how to manually calculate it?

If not, don’t worry! In this post, we will provide guidelines on calculating this barcode and some code 128 barcode check digit calculator that may be helpful for you!

Let’s find out! 

Code 128 check digit calculator

Code 128 check digit calculator

What Is A Check Digit?

A check digit is known as the last digit of all fixed-length to identify errors.

Based on the other numbers in the key, a simple algorithm is used to determine the check digit.

Normally, digital systems can identify changes as data is transported from transmitter to receiver with the use of a check digit.

The binary checksum employed in binary systems has a decimal counterpart known as the check digit. In binary systems, the check digit is the decimal equivalent of the binary checksum.

All GS1 ID Keys, except Component/Part Identifier (CPID) and Global Individual Asset Identifier (GIAI), require a check digit (GIAI). 

The Global Model Number (GMN) has two check characters rather than just one.

A check digit

A check digit

What Is Code 128 Check Digit?

Code 128 barcodes are one-dimensional ("1D") barcode symbols that are widely employed in the identification, inventory, shipping, and supply chains. 

A start bar, the information to be encoded, a check digit, and a stop bar are all parts of a code 128 barcode. 

Also, machine-readable alphanumeric symbols are used in Code 128 barcodes. They can be printed with or without characters to be read by people. 

A subset of Code 128 is, for instance, the GS1-128 barcodes (formerly known as UCC/EAN-128 barcodes). 

In comparison to Code 39 barcodes, they are more compact and occupy less space from left to right.

Code 128

Code 128

Code 128 barcodes have to include the mandatory mod 103 check digit. Before the stop bars, at the conclusion of the input data, is the Code 128 check digit.

The check digit of a Code 128 barcode is dependent on a value assigned to each Code 128 character.

How To Calculate A Code 128 Check Digit Manually?

Because Code 128 is self-checking, a check digit is usually not required. 

On the other hand, a modulo 103 checksum digit may be inserted in applications that demand an exceedingly high level of precision. 

The steps to calculate code 128 check digit are as follows:

  • Step 1: Obtain the corresponding symbol character value.

  • Step 2: A weighting is assigned to each symbol character place. The starting character position is weighted 1. Following that, weights of 1, 2, 3, 4,..., n are applied to additional locations starting at the left with the first symbol character.

  • Step 3: Multiply each character by how much of the barcode string it represents.

  • Step 4: Combine the results of the calculations from step 3.

  • Step 5: The goods' combined total is then divided by 103.

  • Step 6: The value of the residual in step 4 is the symbol check character. Then, based on its ASCII value, you should locate the associated checksum digit.

Calculate a Code 128 check digit manually

Calculate a Code 128 check digit manually

What Is Code 128 Check Digit Calculator?

In case manually calculating a Code 128 check digit is too difficult, you may go for these 2 helpful code 128 check digit calculator online covered below!

GS1 check digit calculator

A barcode number's last digit is a computed check digit.

Any scanning system uses the check digit to determine whether the number scanned in from a barcode is accurate. It is computed from all the previous digits.

With the help of this GS1 Check Digit Calculator, you can obtain the check digit for your GTINs and the 18-digit SSCC required to identify logistical units. 

Simply enter the ID number and this calculator will compute the last digit for you.

You can also use it as a Code128 barcode generator.

GS1 check digit calculator

GS1 check digit calculator

Barcode Graphics

This free GTIN Check Digit Calculator is provided by Bar Code Graphics, Inc.  

They are the top provider of GS1 support services in the US and are specialists in developing and implementing barcodes.

The calculator will calculate the right check digit for all GTIN identifying methods. Just enter the ID number, and this calculator will calculate the last digit for you. 

Furthermore, it can generate GS1-128 barcode depending on your needs!

Barcode Graphics

Barcode Graphics

Frequently Asked Questions (FAQs)
1. How many digits is a barcode 128?

There are 108 symbols total in code 128: 103 data symbols, 3 start symbols, and 2 stop symbols. Each sign is made up of three black bars and three spaces that are different lengths of white.

2. What is the check digit in 13 digit UPC?

A UPC barcode number's final digit is a computer check digit that ensures the barcode is correctly assembled.

3. What is Code 128 format?

Code 128 is a high-density linear barcode system. It is used for barcodes that are just alphanumeric or numerical. 

It can encode all 128 ASCII characters as well as Latin-1 characters using the extension symbol (FNC4).


In conclusion, Code 128 barcodes are widely utilized in the ID, inventory, shipping, and distribution chains. So, we hope that this post has helped you learn more about check digits and that using the code 128 check digit calculator has been helpful to you.

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