What causes file size to suddenly grow??

IMO, one of the common reasons for this is the used range. Deleting the rows to the right of and below the data can substantially reduce the file size.

You might also try the ExcelDiet code here:

http://www.mrexcel.com/board2/viewtopic.php?t=125196

A lot of things can do it.

A lot of complex formulas, applying formatting to unnecessry ranges, etc.

Check out http://www.decisionmodels.com/optspeedb.htm for some tips.

There's also this bit of code that will help reduce bloat:

<font face=tahoma><SPAN style="color:#00007F">Sub</SPAN> WorkbookReducer()
    <SPAN style="color:#007F00">'From: http://www.contextures.com/xlfaqApp.html#Unused</SPAN>
    <SPAN style="color:#007F00">' Re-set used range</SPAN>
    
    <SPAN style="color:#00007F">Dim</SPAN> myLastRow <SPAN style="color:#00007F">As</SPAN> <SPAN style="color:#00007F">Long</SPAN>
    <SPAN style="color:#00007F">Dim</SPAN> myLastCol <SPAN style="color:#00007F">As</SPAN> <SPAN style="color:#00007F">Long</SPAN>
    <SPAN style="color:#00007F">Dim</SPAN> wks <SPAN style="color:#00007F">As</SPAN> Worksheet
    <SPAN style="color:#00007F">Dim</SPAN> dummyRng <SPAN style="color:#00007F">As</SPAN> Range
        
        <SPAN style="color:#00007F">For</SPAN> <SPAN style="color:#00007F">Each</SPAN> wks <SPAN style="color:#00007F">In</SPAN> ActiveWorkbook.Worksheets
            <SPAN style="color:#00007F">With</SPAN> wks
                myLastRow = 0
                myLastCol = 0
                <SPAN style="color:#00007F">Set</SPAN> dummyRng = .UsedRange
                <SPAN style="color:#00007F">On</SPAN> <SPAN style="color:#00007F">Error</SPAN> <SPAN style="color:#00007F">Resume</SPAN> <SPAN style="color:#00007F">Next</SPAN>
                myLastRow = _
                    .Cells.Find("*", after:=.Cells(1), _
                    LookIn:=xlFormulas, lookat:=xlWhole, _
                    searchdirection:=xlPrevious, _
                    searchorder:=xlByRows).Row
                    myLastCol = _
                    .Cells.Find("*", after:=.Cells(1), _
                    LookIn:=xlFormulas, lookat:=xlWhole, _
                    searchdirection:=xlPrevious, _
                    searchorder:=xlByColumns).Column
                <SPAN style="color:#00007F">On</SPAN> <SPAN style="color:#00007F">Error</SPAN> <SPAN style="color:#00007F">GoTo</SPAN> 0
                
                <SPAN style="color:#00007F">If</SPAN> myLastRow * myLastCol = 0 <SPAN style="color:#00007F">Then</SPAN>
                        .Columns.Delete
                    <SPAN style="color:#00007F">Else</SPAN>
                        .Range(.Cells(myLastRow + 1, 1), _
                        .Cells(.Rows.Count, 1)).EntireRow.Delete
                        .Range(.Cells(1, myLastCol + 1), _
                        .Cells(1, .Columns.Count)).EntireColumn.Delete
                <SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">If</SPAN>
            <SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">With</SPAN>
        <SPAN style="color:#00007F">Next</SPAN> wks

<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">Sub</SPAN>
</FONT>

Hope that helps,

Smitty

That's works if the file is still open but....

What happened was I made a few cosmetic changes to the look of the sheet, saved it and closed it. Later when I tried to open it again, it wouldn't open....that's when I opened Explorer and saw the filesize. I have a feeling that I'm past the point of no return in an instance like this.