What is a Check Digit and a Check Digit Calculator?
The last digit of all numeric fixedlength GS1 Identification (ID) Keys is a check digit, which is required and ensures the integrity of the key. The last digit, being the check digit, is calculated using a simple algorithm based on the preceding numbers in the key. The result is an accurately constructed and scannable barcode.
This page provides information for each GS1 ID Key, shows how the calculator works and even provides you step by step instructions on how to manually calculate the check digit by using the simple algorithm, should the need arise.
The four different formats of GTIN include GTIN8, GTIN12, GTIN13 and GTIN14.
Enter 17 digits to calculate the 18th digit, which is the check digit.
Enter 12 digits to calculate the 13th digit, which is the check digit.
The check digit is calculated using a simple algorithm, based on the numbers preceding the check digit of the key.
A step by step algorithm with examples of 1 number without the check digit, the calculations and end result the number with the check digit.
Step 1: Multiply, Step 2: Add, and Step 3 Subtract.
ID Key Format 
Digit Positions 


GTIN8 










N_{1} 
N_{2} 
N_{3} 
N_{4} 
N_{5} 
N_{6} 
N_{7} 
N_{8} 

GTIN12 






N_{1} 
N_{2} 
N_{3} 
N_{4} 
N_{5} 
N_{6} 
N_{7} 
N_{8} 
N_{9} 
N_{10} 
N_{11} 
N_{12} 

GTIN13 





N_{1} 
N_{2} 
N_{3} 
N_{4} 
N_{5} 
N_{6} 
N_{7} 
N_{8} 
N_{9} 
N_{10} 
N_{11} 
N_{12} 
N_{13} 

GTIN14 




N_{1} 
N_{2} 
N_{3} 
N_{4} 
N_{5} 
N_{6} 
N_{7} 
N_{8} 
N_{9} 
N_{10} 
N_{11} 
N_{12} 
N_{13} 
N_{14} 

SSCC 
N_{1} 
N_{2} 
N_{3} 
N_{4} 
N_{5} 
N_{6} 
N_{7} 
N_{8} 
N_{9} 
N_{10} 
N_{11} 
N_{12} 
N_{13} 
N_{14} 
N_{15} 
N_{16} 
N_{17} 
N_{18} 

Step 1: Multiply value of each position by 


x3 
x1 
x3 
x1 
x3 
x1 
x3 
x1 
x3 
x1 
x3 
x1 
x3 
x1 
x3 
x1 
x3 

Step 2: Add results together to create sum 

Step 3: Subtract sum from the next highest multiple of ten = Check digit 
Positions 
N_{1} 
N_{2} 
N_{3} 
N_{4} 
N_{5} 
N_{6} 
N_{7} 
N_{8} 
N_{9} 
N_{10} 
N_{11} 
N_{12} 
N_{13} 

Number without check digit 












 
Step 1: Multiply 
x 
x 
x 
x 
x 
x 
x 
x 
x 
x 
x 
x 
 
by 
1 
3 
1 
3 
1 
3 
1 
3 
1 
3 
1 
3 
 
Step 2: Add results 
= 
= 
= 
= 
= 
= 
= 
= 
= 
= 
= 
= 
 
to create sum 
6 
6 
9 
3 
0 
12 
1 
15 
0 
0 
2 
3 
= 57 
Step 3: Subtract sum from next highest multiple of ten = 60  57 = 3 (check digit) 

Number with check digit 
6 
2 
9 
1 
0 
4 
1 
5 
0 
0 
2 
1 
3 