Reducing File Size

It is a common practice to save excel files as .xlsb (Excel Binary Workbook) in order to reduce the size. This is a relatively new extension but it is becoming a very popular one.
To learn more about .xlsb format see link below

http://blog.datasafexl.com/excel-art...binary-format/

As Amanda has suggested, formatting can play a big part in file size.

Also, it is often related to formulae or blank cells being copied down the entire worksheet; or formatting; or Conditional Formatting. If you do use Conditional Formatting extensively, deleting and adding rows can break up the CF rules which take a lot of processing.

The first thing that I would try is to press Ctrl-End on each worksheet and see where it ends up. If it is way beyond the actual data, then you need to delete excess rows and columns. Select all the rows after the live data and delete them using the Delete icon on the ribbon rather than the Delete key. Similarly with columns.

I would be inclined to re-create all the Pivot Tables from scratch. That said, if you've cleaned up the data, it might be worth copy the data sheets to a new workbook and starting afresh there. Clean workbook ... clean start. And it gives you a backup should you get anything wrong

Reason behind large file size :
> File type : If file extention .xlsx save it as an Excel Binary Worksheet (.xlsb)
>Unused / blank column & row. Kindly delete those. (Locate CTRL + END cell on each worksheet)
>Remove Conditional Formatting.
>Which formulas use. Formulas like SUMPRODUCT SUMIF and VLOOKUP or HLOOKUP tend to increase the size and slow down the workbook.
>Pictures: Do you have any images in your file?
>Pivot Tables: Pivot Tables store the underlying data so (depending on the number of Pivot Tables) in worst case, each Pivot Table contains the data set.
>File link with others.