var sheet = workbook.Worksheets[0];
var pivot = workbook.Worksheets[0].PivotTables[0];
// TableRange1 returns complete Pivot Table area except page fields
var tableRange1 = pivot.TableRange1;
int sRow = tableRange1.StartRow;
int sCol = tableRange1.StartColumn;
int eRow = tableRange1.EndRow;
int eCol = tableRange1.EndColumn;
//Get total number of rows in PivotTable report.
int numRows = eRow - sRow + 1;
//Get total number of cols in PivotTable report.
int numCols = eCol - sCol + 1;
//Get the last (farthest) row index in the worksheet (general) - zero based;
int mRowIndex = sheet.Cells.MaxDataRow;
//Get the last (farthest) column index in the worksheet (general) - zero based;
int mColIndex = sheet.Cells.MaxDataColumn;
Hope, this helps a bit.
Thank you.