A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
As suggested, go to the first blank row, press CTRL-SHIFT-DOWN ARROW, right-click and choose DELETE.
Save the file, size should go down.
If it is still large then go to the first blank column, press CTRL-SHIFT-RIGHT ARROW, right-click and choose DELETE. Save the file.
Sometimes I have to use SAVE AS and overwrite the file. Suggest you save with another name and see.
You will still see blank rows and columns but they are just displayed by Excel and do not take any space in the file.