UPC version A check digit calculator in Excel
Azalea_UPC_A_checkDigit
Copyright 2009 Azalea Software, Inc. All rights reserved. www.azalea.com


The macro in this spreadsheet calculates the UPC version A check digit for an 11-digit input. If you have a company prefix assigned by GS1 and a product number you can calculate the UPC check digit.

Because this spreadsheet is built around a macro, you *must* enable macros for this spreadsheet to work! The .xls file is for Excel 2003 and the .xlsm is for Excel 2007. An alternative is to use a User Defined Function as an .xla (Excel 2003) or .xlam (Excel 2007).

Press ALT-F11 to view the macro in the Visual Basic Editor.

To add the macro to your own spreadsheet:
  Tools/Macro/Visual Basic Editor
  Insert/Module
  Paste in the macro code
  Close the Visual Basic Editor

When you return to your spreadsheet, a new User Defined function is available: Azalea_UPC_A_checkDigit

UPCTools prints UPC, ISBN-13, EAN, JAN, and ISSN barcodes. Available for Windows, OS X, Linux/UNIX, et al. Free sample code and free tech support. Buy online and download immediately.

www.azalea.com/UPC


Function Azalea_UPC_A_checkDigit(ByVal UPCnumber As String) As String
' UPCTools 16mar09 jwhiting
' Copyright 2009 Azalea Software, Inc. All rights reserved. www.azalea.com

' Calculating the UPC version A checkdigit in Excel 2003
' Your input, UPCnumber, is a string consisting of an 11-digit number.
' That is, you don't need the check digit. With or without works.
  
    Dim checkDigitSubtotal As Integer  ' a check digit throwaway

  ' Possible valid input includes 11-digits (no check digit), 12-digits (with check digit), or 14-digits (GTIN).
  Select Case Len(UPCnumber)
    Case 11
      ' We're going to do the UPC check digit calculation because the input doesn't have it.
    Case 12
      ' Let's strip your check digit and calculate ours from scratch. (Nothing personal.)
       UPCnumber = Left(UPCnumber, 11)
   Case 14
      ' GTIN input, but we're going to strip the leading 2 and the last characters to extract the 11-digit input without check digit.
      UPCnumber = Mid(UPCnumber, 3, 11)
   Case Else
      ' Your error handling goes here...
   End Select
    
  ' Now we need to do the UPC A check digit calculation.
  ' Add up the numbers in the odd positions left to right. Multiple the result by 3.
  ' Add up the numbers in the even positions. Now add the first subtotal to the second.
  ' The UPC barcode check digit is the single digit number makes the total a multiple of 10.
checkDigitSubtotal = (Val(Left(UPCnumber, 1))) + (Val(Mid(UPCnumber, 3, 1))) + (Val(Mid(UPCnumber, 5, 1))) + (Val(Mid(UPCnumber, 7, 1))) + (Val(Mid(UPCnumber, 9, 1))) + (Val(Right(UPCnumber, 1)))
checkDigitSubtotal = (3 * checkDigitSubtotal) + (Val(Mid(UPCnumber, 2, 1))) + (Val(Mid(UPCnumber, 4, 1))) + (Val(Mid(UPCnumber, 6, 1))) + (Val(Mid(UPCnumber, 8, 1))) + (Val(Mid(UPCnumber, 10, 1)))

  Azalea_UPC_A_checkDigit = Right(Str(300 - checkDigitSubtotal), 1)

  ' Excel: B1=Azalea_UPC_A_checkDigit(A1)
  ' Or put another way, yourContainer.text=Azalea_UPC_A_checkDigit(yourInputString)
  
End Function