For use in my Units spreadsheet (Units4Excel) I want to extract the unit conversion values from the comprehensive Wikipedia unit conversion table.

On Wikipedia the table looks like this:

and when copied and pasted as Unicode text into Excel, like this:

To convert the text in the final column to values the following changes are required:

• Skip the leading non-numeric characters,
• Remove spaces between numbers.
• Remove the final numbers enclosed in brackets, indicating the uncertainty in the final digits.
• Convert the exponent (e.g. x10-27) to Excel format (E-27). Note that a positive exponent displays as a 4 digit number, e.g. x1027.
• Convert the resulting text string to a number with double data type.
• Extract the units
• Skip references to notes.

The following code does the job:

Function ExtractVal(Txt As String, Optional ExtractUnits As Boolean = True)
' Extract number and optionally units from Wikipedia unit conversion factor table
' Remove preceding text and trailing notes, and variance value enclosed in ()
' Convert x10nn to Enn or x10-nn to E-nn
Dim n As Long, m As Long, char As String, ValStr As String, RtnA() As Variant, i As Long, strcode As Long

' Skip over any non-numeric text before the first number
    If ExtractUnits Then
        ReDim RtnA(1 To 2)
    Else
        ReDim RtnA(1 To 1)
    End If
    n = Len(Txt)
    
    For i = 1 To n
        char = Mid(Txt, i, 1)
        If IsNumeric(char) Then Exit For
    Next i
    ValStr = char
    m = i + 1
    
 ' Extract all numbers until the first non-numeric text
 ' Skip over single spaces followed by a number
    For i = m To n
        char = Mid(Txt, i, 1)
        If IsNumeric(char) = False And char <> "." Then
            If IsNumeric(Mid(Txt, i + 1, 1)) = False Or char <> " " Then Exit For
        Else
            ValStr = ValStr & char
        End If
    Next i
    m = i + 1
    
' Skip over numbers enclosed in ()
    char = Mid(Txt, i, 1)
    If char = "(" Then
        For i = m To n
            char = Mid(Txt, i, 1)
            If char = ")" Then
                i = i + 1
                Exit For
            End If
        Next i
    End If

' Extract numbers following 'x10' and add to value string as Enn
' The 'x' in the Wikipedia table is Ascii code 215
    char = Mid(Txt, i, 1)
    strcode = Asc(char)
    If strcode = 215 Then
        m = i + 3
        ValStr = ValStr & "E"
        For i = m To n
            char = Mid(Txt, i, 1)
            strcode = Asc(char)
            If strcode = 45 Then char = "-"
            If IsNumeric(char) = False And char <> "-" Then Exit For
            ValStr = ValStr & char
        Next i
    End If
 ' Convert value string to double and copy to RtnA
    RtnA(1) = CDbl(ValStr)
    
 ' Extract unit text, skip over final note reference
    If ExtractUnits Then
        m = i + 1
        ValStr = ""
        For i = m To n
            char = Mid(Txt, i, 1)
            If char = "[" Then Exit For
            ValStr = ValStr & char
        Next i
        ' Copy unit to RtnA
        RtnA(2) = ValStr
    End If
    
    ExtractVal = RtnA
End Function

This function can be applied to the text at the top of the final column, and copied down, resulting in:

Columns AB and AC are the function output. Column AD uses the built in IsNumber function to confirm that the values in Column AB are indeed valid numbers.