ISBN-13 to ISBN-10

15 Comments

• Thanks for this! I translated it into Ruby if anyone's interested:
  
  
  
  def isbn_13_to_isbn_10(isbn13)
  isbn10 = isbn13[3,9]
  checksum = 0
  weight = 10
  isbn10.each_char do |c|
  checksum += (c.to_i * weight)
  weight -= 1
  end
  checksum = 11-(checksum % 11)
  if (checksum == 10)
  isbn10 += "X"
  elsif (checksum == 11)
  isbn10 += "0"
  else
  isbn10 += checksum.to_s
  end
  isbn10
  end
  
  

• This is just what I was looking for, well sort of. I need to translate it into VBA for an Excel form. I came up with the following, but it keeps throwing errors...
  'The ISBN-10 equals the ISBN 13 between the 4th and penultimate characters
  isbn10 = OrigISBN.Substring(3, 9)
  'Declare the starting values
  
  checksum = 0
  Weight = 10
  
  'Loop through ISBN-10 adjusting checksum for each character, in order to recalculate the check digit
  For i = 1 To 10
  checksum = checksum + ((Mid(isbn10, i, 1)) * Weight)
  Weight = Weight - 1
  Next i
  
  checksum = 11 - (checksum Mod 11)
  If checksum = 10 Then
  isbn10 = isbn10 & "X"
  ElseIf checksum = 11 Then
  isbn10 = isbn10 & "0"
  Else: isbn10 = isbn10 & checksum
  End If
  isbn10TextBox.Text = isbn10
  
  
  End Sub
  

• Hi,
  
  there is an error on the algo at this line :
  
  String myIsbn10 = theIsbn13.substring(3, 9);
  
  Indeed, the second number must be 12 instead of 9 : You have to remove only the first 3 numbers and the last digit from the isbn-13.
  
  Thanks for all.
  

• Another comment to complete this function. It read that ISBN-13 starting with 979 can't be converted into ISBN-10. So add into the function a line to check if the ISBN-13 we have to convert start with "979" and threw an exception if it is the case :
  
  // --- Check if current ISBN-13 not start with 979
  // ---(can't be converted to ISBN-10)
  if ( theIsbn13.startsWith("979") )
  throw new EngineException("Can't format isbn 13 to 10 starting with 979");
  
  The function should be now complete.
  

• Thanks!
  
  Here is a visual basic version that works fine:
  
  Public Function Isbn13to10(isbn13 As String) As String
  
  
  isbn10 = Mid(isbn13, 4, 9)
  Dim checksum
  checksum = 0
  Dim weight
  weight = 10
  
  For i = 1 To Len(isbn10)
  checksum = checksum + ((Mid(isbn10, i, 1)) * weight)
  
  weight = weight - 1
  
  Next i
  
  checksum = 11 - (checksum Mod 11)
  
  If checksum = 10 Then
  isbn10 = isbn10 & "X"
  Else
  If checksum = 11 Then
  isbn10 = isbn10 & "0"
  Else
  isbn10 = isbn10 & checksum
  End If
  End If
  
  Isbn13to10 = isbn10
  
  End Function
  

• Ok, sorry for flooding this page, but again, ignore the previous code. I promise you, this is the last time (because I've now perfected my code, and removed all bugs).
  
  Option Strict On
  Option Explicit On
  Module Module1
  
  Dim sISBN13 As String = ""
  Dim sISBN10 As String = ""
  
  Function bVerifySum13(ByRef usISBN13 As String) As Boolean
  Dim iMax, iSum As Integer
  bVerifySum13 = True
  iMax = 0
  If usISBN13 Like "#############" Then
  For j As Integer = 2 To 12 Step 2
  iMax += ((Convert.ToInt32(Mid(usISBN13, (j - 1), 1))) + (3 * (Convert.ToInt32(Mid(usISBN13, j, 1)))))
  Next
  iSum = (10 - (iMax Mod 10)) Mod 10
  If iSum Convert.ToInt32(Mid(usISBN13, 13, 1)) Then
  bVerifySum13 = False
  End If
  Else
  bVerifySum13 = False
  End If
  End Function
  
  Function bVerifySum10(ByRef usISBN10 As String) As Boolean
  Dim iMax As Integer = 0
  bVerifySum10 = True
  If usISBN10 Like "##########" Or usISBN10.Length = 10 And Mid(usISBN10, 1, 9) Like "#########" And Mid(usISBN10, 10, 1) = "x" Then
  For j = 10 To 2 Step -1
  iMax += ((Convert.ToInt32(Mid(usISBN10, (10 - (j - 1)), 1))) * j)
  Next
  If Mid(usISBN10, 10, 1) "x" Then
  iMax += Convert.ToInt32(Mid(usISBN10, 10, 1))
  Else
  iMax += 10
  End If
  If (iMax Mod 11) 0 Then
  bVerifySum10 = False
  End If
  Else
  bVerifySum10 = False
  End If
  End Function
  
  Function sConvertN10toN13(ByRef usISBN10 As String) As String
  Dim iMax As Integer = 0
  sConvertN10toN13 = "978" + Mid(usISBN10, 1, 9)
  For j As Integer = 2 To 12 Step 2
  iMax += (Convert.ToInt32(Mid(sConvertN10toN13, (j - 1), 1))) + (3 * (Convert.ToInt32(Mid(sConvertN10toN13, j, 1))))
  Next
  sConvertN10toN13 += ((10 - (iMax Mod 10)) Mod 10).ToString
  End Function
  
  Function sConvertN13toN10(ByRef usISBN13 As String) As String
  Dim iMax As Integer = 0
  Dim iCount As Integer = 0
  sConvertN13toN10 = Mid(usISBN13, 4, 9)
  For j As Integer = 10 To 2 Step -1
  iMax += ((Convert.ToInt32(Mid(sConvertN13toN10, (10 - (j - 1)), 1))) * j)
  Next
  If (iMax Mod 11) 0 Then
  Do
  iCount += 1
  Loop Until ((iMax + iCount) Mod 11) = 0
  If iCount = 10 Then
  sConvertN13toN10 += "x"
  Else
  sConvertN13toN10 += iCount.ToString
  End If
  Else
  sConvertN13toN10 += "0"
  End If
  End Function
  
  Sub Main()
  Dim sInputChoice As String = ""
  Call shameless_plug()
  Call DisplayOptions()
  Do
  Call Console.Write("?: ")
  sInputChoice = Console.ReadLine()
  Select Case sInputChoice
  Case "quit"
  End
  Case "disp"
  Call DisplayOptions()
  Case "10"
  Call InterfaceISBN10()
  Case "13"
  Call InterfaceISBN13()
  Case "10to13"
  Call InterfaceISBN10ToISBN13()
  Case "13to10"
  Call InterfaceISBN13ToISBN10()
  Case Else
  Call Console.WriteLine("Invalid option")
  End Select
  Loop
  End Sub
  
  Sub InterfaceISBN10()
  Call Console.WriteLine()
  Call Console.WriteLine("ISBN-10 Validation")
  Call Console.WriteLine("(To exit back to main menu, type 'r' and hit return)")
  Do Until sISBN10 = "r"
  Call Console.Write("?10: ")
  sISBN10 = Console.ReadLine()
  sISBN10 = sISBN10.ToLower
  If sISBN10 "r" And bVerifySum10(sISBN10) True Then
  Call Console.WriteLine("Invalid ISBN-10 number")
  ElseIf sISBN10 "r" And bVerifySum10(sISBN10) = True Then
  Call Console.WriteLine("Valid ISBN-10 number")
  End If
  Loop
  Call Console.WriteLine()
  Call DisplayOptions()
  End Sub
  
  Sub InterfaceISBN13()
  Call Console.WriteLine()
  Call Console.WriteLine("ISBN-13 Validation")
  Call Console.WriteLine("(To exit back to main menu, type 'r' and hit return)")
  Do Until sISBN13 = "r"
  Call Console.Write("?13: ")
  sISBN13 = Console.ReadLine()
  sISBN13 = sISBN13.ToLower
  If sISBN13 "r" And bVerifySum13(sISBN13) True Then
  Call Console.WriteLine("Invalid ISBN-13 number")
  ElseIf sISBN13 "r" And bVerifySum13(sISBN13) = True Then
  Call Console.WriteLine("Valid ISBN-13 number")
  End If
  Loop
  Call Console.WriteLine()
  Call DisplayOptions()
  End Sub
  
  Sub InterfaceISBN10ToISBN13()
  Call Console.WriteLine()
  Call Console.WriteLine("ISBN10 to ISBN13 conversion")
  Call Console.WriteLine("(To exit back to the main menu, type 'r' and hit return)")
  Do
  Call Console.Write("?10: ")
  sISBN10 = Console.ReadLine()
  sISBN10 = sISBN10.ToLower
  If sISBN10 "r" And bVerifySum10(sISBN10) True Then
  Call Console.WriteLine("Invalid input")
  ElseIf sISBN10 "r" And bVerifySum10(sISBN10) = True Then
  Call Console.WriteLine("As an ISBN13 number, this is " + sConvertN10toN13(sISBN10))
  Call System.Threading.Thread.Sleep(1200)
  Call Console.WriteLine("Verification of newly converted ISBN13 number...")
  Call System.Threading.Thread.Sleep(300)
  If bVerifySum13(sConvertN10toN13(sISBN10)) True Then
  Call Console.WriteLine("Oops, it seems that this is invalid")
  Else
  Call Console.WriteLine("Everything A-OK")
  End If
  End If
  Loop Until sISBN10 = "r"
  Call Console.WriteLine()
  Call DisplayOptions()
  End Sub
  
  Sub InterfaceISBN13ToISBN10()
  Call Console.WriteLine()
  Call Console.WriteLine("ISBN13 to ISBN10 conversion")
  Call Console.WriteLine("(To exit back to the main menu, type 'r' and hit return)")
  Do
  Call Console.Write("?13: ")
  sISBN13 = Console.ReadLine()
  sISBN13 = sISBN13.ToLower
  If sISBN13 "r" And bVerifySum13(sISBN13) True Then
  Call Console.WriteLine("Invalid input")
  ElseIf sISBN13 "r" And bVerifySum13(sISBN13) = True Then
  Call Console.WriteLine("As an ISBN10 number, this is " + sConvertN13toN10(sISBN13))
  Call System.Threading.Thread.Sleep(1200)
  Call Console.WriteLine("Verification of newly converted ISBN10 number...")
  Call System.Threading.Thread.Sleep(300)
  If bVerifySum10(sConvertN13toN10(sISBN13)) True Then
  Call Console.WriteLine("Oops, it seems that this is invalid")
  Else
  Call Console.WriteLine("Everything A-OK")
  End If
  End If
  Loop Until sISBN13 = "r"
  Call Console.WriteLine()
  Call DisplayOptions()
  End Sub
  
  Sub DisplayOptions()
  Call Console.WriteLine("Options:")
  Call Console.WriteLine("10 - ISBN10 validation")
  Call Console.WriteLine("13 - ISBN13 validation")
  Call Console.WriteLine("10to13 - ISBN10 to ISBN13 conversion")
  Call Console.WriteLine("13to10 - ISBN13 to ISBN10 conversion")
  Call Console.WriteLine("disp - display these options")
  Call Console.WriteLine("quit - exit this program")
  End Sub
  
  Sub shameless_plug()
  Call Console.WriteLine("Z-130 version pi")
  Call Console.WriteLine("Written by Zero-Hero")
  Call Console.WriteLine("License: Public Domain")
  Call Console.WriteLine()
  Call Console.WriteLine("This program does the following:")
  Call Console.WriteLine("1) Convert (either way) between ISBN10 and ISBN13, at your choice")
  Call Console.WriteLine("2) Check the validity of either an ISBN10 or ISBN13 number, at your choice")
  Call Console.WriteLine()
  Call Console.WriteLine("This program will NOT do the following:")
  Call Console.WriteLine("1) Make girls like you")
  Call Console.WriteLine("2) Make men like you")
  Call Console.WriteLine()
  Call Console.Write("Press enter to continue")
  Call Console.ReadLine()
  Call Console.WriteLine()
  End Sub
  
  End Module
  
  

• There is a slight error in the code, which will cause problems for ISBNs with Xs on the end.
  
  In the PHP on about Line 13
  
  $isbn10 += "X";
  
  Should be something like
  
  $isbn10 = $isbn10 . "X";
  
  Because PHP appends with '.' not '+'.
  
  The line below that also looks suspicious, the one with the 0, although I haven't had any problems caused by it, I'm going to change it in my code.
  
  Anyway, if anyone is having strange errors, hopefully the function below will help solve it:
  
  function isbn13_to_isbn10($isbn13) {
  $isbn13 = trim($isbn13);
  $isbn13 = str_replace("-","",$isbn13);
  $isbn13 = str_replace(" ","",$isbn13);
  $isbn10 = substr($isbn13,3,9);
  $checksum = 0;
  $weight = 10;
  $isbnCharArray = str_split($isbn10);
  foreach($isbnCharArray as $char) {
  $checksum += $char * $weight;
  $weight--;
  }
  $checksum = 11-($checksum % 11);
  if ($checksum == 10) { $isbn10 = $isbn10 . "X"; }
  else if ($checksum == 11) { $isbn10 += "0k"; }
  else $isbn10 .= $checksum;
  return $isbn10;
  }
  

• Thanks for the code examples.
  
  Actually Amazon does support ISBN-13, but tagged as EAN (if you parse AWS XML response).
  And ISBN still means ISBN-10.
  

• can someone post the VB net function to convert from ISBN 10 TO 13 instead?
  
  thanks.
  
  

• Thank you... this is what we're looking for.....
  

• Hey Guys,
  
  Great work. The comment Philip Kimmey is really useful and a very important modification. I had the problem with that kind of ISBN-13 number. Now it is solved. Thanks to Philip Kimmey.
  
  Cheers.
  

• SQL Server UDF (User Defined Function)
  
  
  /*
  Description: Converts a 13 digit ISBN to a 10 digit ISBN
  
  */
  CREATE FUNCTION [dbo].[ConvertISBN13_To_10](@in_ISBN VARCHAR(20))
  
  RETURNS VARCHAR(20)
  
  AS
  
  
  BEGIN
  
  --VARS
  DECLARE @wf INT; SET @wf = 10;
  DECLARE @CurrentDigit INT; SET @CurrentDigit = 1;
  DECLARE @iTotal INT; SET @iTotal = 0;
  DECLARE @IsbnDigit INT; SET @IsbnDigit = 0;
  DECLARE @Leftover INT; SET @Leftover = 0;
  DECLARE @ISBN10_NoChk VARCHAR(9)
  DECLARE @ISBN10 VARCHAR(20)
  DECLARE @Error BIT; SET @Error = 0;
  
  --make sure it's a 978 13 digit ISBN, if not, just return what was passed in
  IF(LEN(@in_ISBN) = 13 AND SUBSTRING(@in_ISBN, 1, 3) = '978')
  BEGIN
  --drop the ISBN13 check digit and prefix
  SET @ISBN10_NoChk = SUBSTRING(@in_ISBN, 4, 9)
  
  --loop to find the conversion sum
  WHILE (@CurrentDigit < 10 AND @Error = 0)
  BEGIN
  --get the current digit (make sure it's numeric)
  IF(CAST(SUBSTRING(@ISBN10_NoChk, @CurrentDigit, 1) AS VARBINARY) between 0x30 and 0x39)
  BEGIN
  SET @IsbnDigit = CAST(SUBSTRING(@ISBN10_NoChk, @CurrentDigit, 1) AS INT)
  
  --add the weighted value to the conversion sum
  SET @iTotal = @iTotal + (@IsbnDigit * (@wf - @CurrentDigit + 1));
  
  
  --move to the next digit in the ISBN
  SET @CurrentDigit = @CurrentDigit + 1
  END
  ELSE --found an alpha, cancel conversion
  BEGIN
  SET @Error = 1
  SET @ISBN10 = @in_ISBN
  END
  END
  
  --if no error, find the mod (remainder) for the conversion
  IF(@Error = 0)
  BEGIN
  --get the leftover
  SET @Leftover = @iTotal % 11;
  
  --Create ISBN13 (if check digit = 10 convert to '0')
  IF(@Leftover = 0)
  SET @ISBN10 = @ISBN10_NoChk + '0'
  ELSE
  BEGIN
  IF((11 - @Leftover) = 10)
  SET @ISBN10 = @ISBN10_NoChk + 'X'
  ELSE
  SET @ISBN10 = @ISBN10_NoChk + CAST((11 - @Leftover) AS VARCHAR(2))
  END
  END
  END
  ELSE --Bad ISBN, cancel conversion
  BEGIN
  SET @ISBN10 = @in_ISBN
  END
  
  --output results
  RETURN @ISBN10
  
  END
  
  GO
  

• When I run the PHP version and the ISBN-10 number ends in zero the zero is removed and it becomes a 9 digit #. I'm not a programmer so I'm unable to figure out what is wrong.
  

• any updates on the following?
  
  When I run the PHP version and the ISBN-10 number ends in zero the zero is removed and it becomes a 9 digit #. I'm not a programmer so I'm unable to figure out what is wrong.
  
  

• this was the fix for php. it was that 'k' next to the '0':
  
  //$isbn10 += "0k";
  
  $isbn10 .= "0";