C# Calculate how long it will take a loop to finish : So i have the following loop:

    for (int i = 1; i < numRows + 2; i++) //numRows was +4, now +2
            {
                
                Console.Clear();

                Console.WriteLine("Number of rows: " + numRows);
                Console.Write("Checking Row #: " + currRowNumber);

                //We want to skip every row that is null and continue looping until we have more than 3 rows in a row that are null, then break
                if (i > 1)
                {
                    i -= 1;
                }

                //Create Worksheet Range
                Microsoft.Office.Interop.Excel.Range range = (Microsoft.Office.Interop.Excel.Range)excelWorkbookWorksheet.Cells[i, 2];
                string cellValue = Convert.ToString(range.Value);
               
                if (nullCounter == 3) //was 5
                {
                    Console.WriteLine("\nNull row detected...breaking");
                    Console.WriteLine("Number of rows deleted: " + numRowsDeleted);
                    break;
                }

                if (cellValue != null)
                {
                    if (cellValue.Contains(searchText))
                    {
                        //Console.WriteLine("Deleting Row: " + Convert.ToString(cellValue));
                        ((Range)excelWorkbookWorksheet.Rows[i]).Delete(XlDeleteShiftDirection.xlShiftUp);
                        numRowsDeleted++;
                        //Console.WriteLine("Number of rows deleted: " + numRowsDeleted);
                        nullCounter = 0;
                        i--;
                        currRowNumber++;
                        rowsPerSecond = i;
                    }
                    else
                    {
                        currRowNumber++;
                        nullCounter = 0;
                    }
                }
                else
                {
                    nullCounter++;
                    //Console.WriteLine("NullCounter: " + nullCounter);
                }
                i++;
               
            }

I want to calculate how many rows im looping through per second, then calculate from that number how long it will take to complete the entire loop, based on how many rows there are. 

Again, any help is appreciated, thanks!