This calculator is available as a download in spreadsheet format.
If you want to see this as a Visual Basic function, click here for a good example.

Public Function EAN_UPC_CheckDigit(ByVal Code As String) As Integer
    '
    ' Returns the check digit if given a 11 or 12 digit UPC or EAN number
    ' If the return value is -1 then the code coming in is invalid and
    ' no check digit can be returned.
    '
    Dim x As Integer
    Dim check As Integer
    Dim v1 As Integer
    Dim v2 As Integer
    Dim dig As Integer
    Dim c As Integer
    
    If Len(Code) <> 11 And Len(Code) <> 12 Then
        ' Not the right length for UPC or EAN
        EAN_UPC_CheckDigit = -1
        Exit Function
    End If
    
    c = 0
    If Len(Code) = 11 Then Code = "0" & Code ' Make it 12 digits
    
    For x = 1 To 12
        dig = Asc(Mid(Code, x, 1)) - 48
        If dig < 0 Or dig > 9 Then
            ' Not a digit so it can't be UPC or EAN
            EAN_UPC_CheckDigit = -1
            Exit Function
        End If
        If c = 1 Then
            v1 = v1 + dig
        Else
            v2 = v2 + dig
        End If
        c = 1 - c ' switch between odd and even digits
    Next x
    
    check = v1 * 3 + v2
    
    EAN_UPC_CheckDigit = ((10 - (check Mod 10)) Mod 10)
End Function

What is the difference between UPC-A and UPC-E?

Well the short answer is that UPC-A is a 12 digit code and UPC-E is that same code with 4 of the zero digits removed from the middle to save space. These are often used on smaller packages and often on soda cans. This format is also called zero-suppressed format.

The longer answer is a little more complex and I will try to explain it here. All UPC codes can be displayed using the 12 digit UPC-A format. Not all UPC codes can be displayed using the 8 digit UPC-E format. Why? There are 2 basic rules that determine which codes can be in the UPC-E format. First, the UPC code must use a zero as the Number System Character. Next there must be four zero digits grouped together in the middle section of the full UPC-A code. If the full 12 digit UPC-A code fits these two rules, then it can be reduced to an 8 digit UPC-E code using the following rules...

• First take note that UPC-A can only be converted to UPC-E if the first digit of the UPC-A is a 1 or 0 and there are four zero digits togetehr in the middle of the entire code.
  
  
• If the manufacturer code ends in 000, 100, or 200, the UPC-E code consists of the first two characters of the manufacturer code, the last three characters of the product code, followed by the third character of the manufacturer code. The product code must be 00000 to 00999.
  
  
• If the manufacturer code ends in 00 but does not qualify for #1 above, the UPC-E code consists of the first three characters of the manufacturer code, the last two characters of the product code, followed by the digit "3". The product code must be 00000 to 00099.
  
  
• If the manufacturer code ends in 0 but does not quality for #1 or #2 above, the UPC-E code consists of the first four characters of the manufacturer code, the last character of the product code, followed by the digit "4". The product code must be 00000 to 00009.
  
  
• If the manufacturer code does not end in zero, the UPC-E code consists of the entire manufacturer code and the last digit of the product code. Note that the last digit of the product code must be in the range of 5 through 9. The product code must be 00005 to 00009.

If you are like me, converting from UPC-A to UPC-E is not really all that important. What you want is to go from UPC-E back to the full 12 digits of UPC-A so you have a uniform code to work with. Well, I have VB functions that will convert either direction for you.

• View the UPC-A to UPC-E function (12 digits to 8 digits)
• View the UPC-E to UPC-A function (8 digits back to 12 digits)

How are the EAN-13/UPC-A/UPC-E barcodes created?

The first step when encoding any of the three barcode types is to determine which parity you are going to use. To do this we need to take the first digit from the EAN-13 number, zero if you are encoding UPC-A or the last digit of a UPC-E number. Use the digit you have come up with as the "Parity Digit" and locate your barcode sequences in the table shown below.

• This chart will be a key part in demonstrating
  the encoding of the following three codes...
• EAN-13 code 8592920000342
• UPC-A code 049000000443
• UPC-E code 04904403

You may be thinking that the chart above looks similar something you have seen elsewhere but at the same time very different. Most people talk a lot about the ODD or EVEN parity of the first six digits when they are encoded into the barcode. Personally, I find that quite confusing and hard to work with. The above chart still makes use of the ODD/EVEN parity, it is simply represented in a different manner. The 0 digits represent the ODD parity barcodes and the 1 digits represent the EVEN parity barcodes. The 2 digits represent the digits to the right of the center bar on UPC-A and EAN-13 barcodes. UPC-E has no center bar and only encodes 6 digits.

To meke more sense out of the ODD/EVEN parity, I have simply reduced the process into picking your barcode sequence by finding your parity bit as described above and then using the digits 0, 1 or 2 to choose the proper barcode patterns from the table shown below.

It is very important to note that each digit is made up of seven stripes which represent binary 0 or 1. When two of the same digit are next to each other it simply looks like a wider single stripe but it is really multiple binary digits. The graphics below will make this point rather clear.

Digit To Encode	Pattern 0	Pattern 1	Pattern 2
0
1
2
3
4
5
6
7
8
9

Now we are almost ready to put the barcode together. There are just a couple special patterns that need to be used. These special patterns tell the scanner what part of the barcode is being processed. EAN-13 and UPC-A have the same configuration: GUARD, 6 digits, SPACER, 6 digits, GUARD. The UPC-E is a little different because it only encodes 6 digits: GUARD, 6 digits, UPCESTOP. The table below demostrates the special bar patterns.

Name	Pattern
Guard
SPacer
StopUPCE

Now we have all the parts we need. Lets put together some barcodes so you can see the system in action for real. We will use one of each type of code EAN-13, UPC-A and UPC-E. The UPC-A and UPC-E will be the same code in two different versions.

EAN-13 code 8592920000342

The first digit is 8 so we will use the pattern sequence of 010110222222 to encode the remaining 12 digits into the barcode pattern. The first digit is not encoded. It is implied based on the coding system. In the sample below, the first row shows the numbers to be encoded, the second is the pattern column used to do the encoding and finally the barcode itself. Below the sample is the fully encoded barcode with the digits displayed for humans to read.

	5	9	2	9	2	0		0	0	0	3	4	2
G	0	1	0	1	1	0	SP	2	2	2	2	2	2	G

UPC-A code 049000000443

When encoding UPC-A, we always use 0 as our parity digit because UPC-A is the same as EAN-13 with a leading zero. The leading zero is simply not displayed in the UPC-A format. Using 0 as our parity bit our pattern sequence is set to 000000222222 for the encoding process. With UPC-A, all 12 digits are encoded into the barcode pattern. In the sample below, the first row shows the numbers to be encoded, the second is the pattern column used to do the encoding and finally the barcode itself. Below the sample is the fully encoded barcode with the digits displayed for humans to read.

	0	4	9	0	0	0		0	0	0	4	4	3
G	0	0	0	0	0	0	SP	2	2	2	2	2	2	G

UPC-E code 04904403

In order to create a UPC-E code you must first compress the UPC-A code down using the system described above. Once this is done you use the check digit (the last digit) in conjunction with the first digit (always 0 or 1) to determine the pattern sequence. In this case, the check digit is 3 and the first digit is 0 so we end up with a pattern sequence of 110001 for the encoding process. With UPC-E, only the middle 6 digits are are encoded into the barcode pattern. The first digit and the check digit are implied based on the parity. In the sample below, the first row shows the numbers to be encoded, the second is the pattern column used to do the encoding and finally the barcode itself. Below the sample is the fully encoded barcode with the digits displayed for humans to read.

	4	9	0	4	4	0
G	1	1	0	0	0	1	S

Hopefully now, you can see that what at first glance appears to be a very complex pattern is really rather easy to create using these basic steps. I would hope that you try this yourself. Take a couple products and work out the barcode pattern. Then compare what you have come up with against what is actually printed on the product.

One little side note to those of you trying to print your own UPC/EAN codes on ink jet printers. They aren't as accurate when it comes to creating these repeating patterns of bars and white space. Often if you print too small the lines will be fussy and scanners will have a hard time reading the barcode. Some times, they won't be able to read them at all. If you are using an ink jet printer, make your barcodes a little bigger to be safe. Lazer printers don't have any problems producing small barcodes. At least not that I have found.

What about the digits under the barcode?

Traditionally, EAN-13 only prints the first digit outside of the barcode, slightly higher than the other digits and then places 6 digits on each side of the seperator. UPC-A places the first and last digits outside of the barcode, slightly higher than the other digits and then places 5 digits on each side of the seperator. UPC-E places the first and last digits outside of the barcode, slightly higher than the other digits and the remaining 6 digits inside of the barcode.

This placement of the digits is simply cosmetic and for human consumption. The scanners can't read these numbers. They only read the bars. You could leave the numbers off all together. It isn't a good idea to print a barcode without any text though because if for any reason the scanner can't read the bars, a human will need to type in the numbers. Most people have a hard time decoding the bars without the numbers being displayed under them.

          

If you are creating your own barcodes and you don't care about the presentation being in the exact same format as the traditional barcodes, feel free to place the digits under the barcode in sequence. At least that way the human users will be able to read them if they have to type them in manually. Either of the above barcodes will scan in exactly the same. The only difference is that the barcode on the left has a non-standard human readable format. This won't effect the functionality of the barcode in any way.

UPC Format For Audio/Video Products

The format for Audio/Video products is slightly special. The first 6 digits (C) are still the company code. The next four digits (P) are the product code. The next digit (M) is used to identify the type of media. The last digit (D) is still the check digit.

There doesn't appear to be any way by looking at the code to tell if it is a if the full code is an audio/video code when compaired to other UPC codes. But knowing that the code is an audio/video item, you can use the code to find out what type of media it is.