Minimize the Used Range 

To save memory and reduce file size, Excel tries to store information about only the area on a worksheet that was used. This is called the used range. Sometimes various editing and formatting operations extend the used range significantly beyond the range that you would currently consider used. This can cause performance and file-size impediments.

Let’s clean your used range by clearing the whitespace on the spreadsheet by going over to the real last used cell.  Start out by going to the far right of the spreadsheet, the last column where data ends, and select the column then (Ctrl+Shift+Right Arrow) and choose Clear, Clear All.

Now go back to the first unused cell at the bottom of the first column, press (Ctrl+Shift+Down Arrow) then (Ctrl+Shift+Right Arrow) and choose Clear, Clear All.

Turn Off Auto Calculation

Most spreadsheets have AutoCalc turned on by default. By turning this off, you should see a performance increase, however, you will now need to manually run your formula calculations by selecting F9.             

Select the Formulas tab and then the Calculation Options button and change to Manual.

Turn Off AutoSave

Most spreadsheets have AutoSave turned on by default. By turning this off, you should see a performance increase, however, you will now need to manually save your spreadsheet by selecting the Save option or pressing Ctrl+S.