The SHEET function returns the index number of a sheet in Excel. You can use the SHEET function to get a numeric index that represents the order of sheets in an Excel workbook, starting with 1 on the left and ending with N on the right, where N is the total number of sheets in the workbook. The SHEET function includes hidden sheets in the numbering sequence.
The SHEET function takes one argument, value, which should be a reference, a named range, or an Excel Table. Value is optional. When value is omitted, SHEET will return a numeric index for the current sheet (i.e. the sheet the formula exists in).
For example, in a workbook with Sheet1, Sheet2, and Sheet3 running left to right: