Q & A: What is the Check Digit?
This is the final digit that is calculated from the other digits of some GS1 Identification keys, including the GTIN-12 and GTIN-14. This digit is used to check that the data has been correctly composed.
Q & A: Does GS1 US Data Hub automatically generate the check digit?
Yes, if you click the "Let Us Assign Your GTIN" button, GS1 US Data Hub will incorporate your GS1 Company Prefix, reserve the right number of digits for the Item Reference, and generate the check digit.
If you already know the Item Reference you want to enter for this GTIN, click the "Choose a Specific GTIN" button. Enter the Item Reference, then click the "Get GTIN Check Digit" button. GS1 US Data Hub calculates the check digit for you.
If you already know the GS1 Company Prefix AND the Item Reference but want to learn how to calculate the check digit manually (outside of GS1 US Data Hub), visit the GS1 US Check Digit Calculator page to calculate the check digit.
Q & A: What data should I enter in the Check Digit Calculator?
For a GTIN-12, which is the only GTIN that can be used in a UPC-A barcode, you should enter the following in the the GTIN-12 field:
- U.P.C. Company Prefix (this is found on your GS1 Company Prefix Certificate)
- Item Reference - this makes the GTIN unique from other GTINs you may have created
Note: these two segments make up the first 11 digits of the GTIN-12.
If you are creating a "higher level" shipping/receiving item that contains multiple quantities of a single GTIN (such as an inner pack or case), you should enter the following in the GTIN-14 field:
- Indicator Digit, which consists of a numeric value from 1 to 8
- The same GS1 Company Prefix as the "each" GTIN that makes up the contents of this packaging item
- The same Item Reference as the "each" GTIN that makes up the contents of this packaging item