To hide unused rows in Excel
Taken from this article on TekReview

Make sure to leave room for expansion, if necessary. 


Select the first column to the right of your data. Now we need to select all columns from this starting point to the end of the spreadsheet. Because Excel gives users spreadsheets with tens of thousands of rows and columns, we’ll use keyboard shortcuts to quickly jump to the end.
With the rightmost empty column selected, press and hold the Shift key and then press Command + Right Arrow. This will jump you to the end of the spreadsheet while the Shift key automatically selects every cell in between.
Now we have to tell Excel to hide these cells. With your cells still selected, go to Excel’s Menu Bar and choose Format &gt; Column &gt; Hide. You’ll now see all the cells to the right of your data disappear.
Next, we need to deal with the cells below your data. Similar to the steps above, this time select the first row beneath your data. With the bottommost cell selected, press and hold Shift and then press Command + Down Arrow. This will jump you to the very bottom of the spreadsheet and select all the rows in between.
Finally, head back up to Excel’s Menu Bar and choose Format &gt; Row &gt; Hide. You’re now left with a spreadsheet that features only cells containing your data, resulting in a much cleaner look.




If you need to expand your table, or simply don’t like the new look, you can easily unhide the cells. First, click the top-left heading cell that looks like a white arrow pointing to the bottom-right corner. Clicking this cell will select all cells in your spreadsheet, both hidden and not. Once selected, go to Excel’s Menu Bar and choose both Format &gt; Column &gt; Unhide and Format &gt; Row &gt; Unhide. Your spreadsheet will now be restored to the default look.