All GTINs need a check digit, and this is the last digit of the number.  The check digit is calculated from all the preceding digits, and it is used by any scanning system to check that the number scanned in from a barcode is correct.  This calculator can be used to work out the check digit for your GTINs, and for the 18-digit SSCC (serial shipping container code) used to identify logistics units.

 

Choose the appropriate GTIN or SSCC option from the dropdown list opposite.  The table below explains which GTINs usually appear in which GS1 barcodes.  Remember that a leading zero in front of a GTIN-13 does not change the number, but simply allows it to be printed in a barcode that requires 14-digits, such as an ITF-14 or GS1-128 barcode.

Other GS1 identifiers also need a check digit to complete them, and this calculator can also provide these for the following GS1 keys.

 

Global Location Number (GLN), Global Returnable Asset Identifier (GRAI), Global Coupon Number (GCN), Global Document Type Identifier (GDTI).  These all incorporate, at least, a 13-digit number and the check digit is the same as that for a GTIN-13.

 

Global Service Relation Number (GSRN).  This is an 18-digit number and the check digit is the same as that for an SSCC.

 

Global Shipment Identification Number.  This is a 17 digit number.  Place a leading zero in front of it, and then use the SSCC check digit calculator.

 

For further information about these other GS1 keys mentioned above, please consult the GS1 General Specifications at  http://www.gs1.org/genspecs

How to calculate your check digit yourself

 

Example barcode number: 501234576421

 

Step 1: add together all alternate numbers starting from the right

5 0 1 2 3 4 5 7 6 4 2 1

0 + 2 + 4 + 7 + 4 + 1 = 18

 

Step 2: multiply the answer by 3

18 x 3 = 54

 

Step 3: now add together the remaining numbers

5 0 1 2 3 4 5 7 6 4 2 1

5 + 1 + 3 + 5 + 6 + 2 = 22

 

Step 4: add step 2 and 3 together

54 + 22 = 76

 

Step 5: the difference between step 4 and the next 10th number:

76 + 4 = 80

Check digit = 4