Calculate check digit

How to calculate Check Digit of barcode manually

To calculate the check digit manually you need to do some simple math. You can use the following table.

ID Key Format	Digit positions
GTIN-8											N₁	N₂	N₃	N₄	N₅	N₆	N₇	N₈
GTIN-12							N₁	N₂	N₃	N₄	N₅	N₆	N₇	N₈	N₉	N₁₀	N₁₁	N₁₂
GTIN-13						N₁	N₂	N₃	N₄	N₅	N₆	N₇	N₈	N₉	N₁₀	N₁₁	N₁₂	N₁₃
GTIN-14					N₁	N₂	N₃	N₄	N₅	N₆	N₇	N₈	N₉	N₁₀	N₁₁	N₁₂	N₁₃	N₁₄
SSCC	N₁	N₂	N₃	N₄	N₅	N₆	N₇	N₈	N₉	N₁₀	N₁₁	N₁₂	N₁₃	N₁₄	N₁₅	N₁₆	N₁₇	N₁₈
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 the sum from nearest equal or higher multiple of ten = *Check Digit*

Now we explain in detail how to calculate the check digits of a barcode, (UPC-A barcode in the follow example) without using a check digit generator software.

Step 1

Enter the code in such a way as to leave only one empty space on the left (that it will be space for the check digt).
Example with UPC-A: 12345678901

ID Key Format	Code without Check digit
UPC-A							1	2	3	4	5	6	7	8	9	0	1	Check Digit

Step 2

Multiply each number with the value of the under column.

ID Key Format	Code without Check digit
UPC-A							1	2	3	4	5	6	7	8	9	0	1	Check Digit
	x3	x1	x3	x1	x3	x1	x3	x1	x3	x1	x3	x1	x3	x1	x3	x1	x3
Result							3	2	9	4	15	6	21	8	27	0	3	Check Digit

Step 3

Add the values obtained.

	Sum
Result							3+	2+	9+	4+	15+	6+	21+	8+	27+	0+	3	= 98

Step 4

Subtract the sum from the nearest equal or higher multiple of ten.
In this case 100.

	Substraction
Result															100	–	98	= 2

Step 5

Write the code number with check digit.

ID Key Format	Code with Check digit
UPC-A							1	2	3	4	5	6	7	8	9	0	1	2

The following table gives an example to illustrate how a UPC-A Check Digit is calculated:

Positions	N₁	N₂	N₃	N₄	N₅	N₆	N₇	N₈	N₉	N₁₀	N₁₁	N₁₂
Number *without* Check Digit	1	2	3	4	5	6	7	8	9	0	1	–
Step 1: Multiply	x	x	x	x	x	x	x	x	x	x	x	–
by	3	1	3	1	3	1	3	1	3	1	3	–
Step 2: Add results	=	=	=	=	=	=	=	=	=	=	=	–
to create *sum*	3	2	9	4	15	6	21	8	27	0	3	= 98
Step 3: Subtract the sum from nearest equal or higher multiple of ten = 100- 98 = 2 (Check Digit)
Number *with* Check Digit	1	2	3	4	5	6	7	8	9	0	1	2