# How to calculate a check digit manually

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

GSIN

N1

N2

N3

N4

N5

N6

N7

N8

N9

N10

N11

N12

N13

N14

N15

N16

N17

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

The following table gives an example to illustrate how a GTIN-13 Check Digit is calculated:

Positions

N1

N2

N3

N4

N5

N6

N7

N8

N9

N10

N11

N12

N13

Number without Check Digit

6

2

9

1

0

4

1

5

0

0

2

1

-

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

-

=

=

=

=

=

=

=

=

=

=

=

=

-

to create sum

6

6

9

3

0

12

1

15

0

0

2

3

= 57

Step 3: Subtract the sum from nearest equal or higher multiple of ten = 60- 57 = 3 (Check Digit)

Number with Check Digit

6

2

9

1

0

4

1

5

0

0

2

1