ActiveSheet.UsedRange.Rows.Count + ActiveSheet.UsedRange.Rows(1).Row -1
Short. Safe. Fast. Will return the last non-empty row even if there are blank lines on top of the sheet, or anywhere else. Works also for an empty sheet (Excel reports 1 used row on an empty sheet so the expression will be 1). Tested and working on Excel 2002 and Excel 2010.
