In this article you will learn how to copy formula to every cell in column or row.

Copying values in tables is very easy. Take a look at the picture below. You should only put cursor in the right bottom of the cell and double click.

Copying Example Table

Values insert but only in the cells where there are some neighbors. 

Copying Not Entire Column

But what to do when you want to copy entire column or row? There is a Fill option in the Ribbon in Excel.

Ribbon Fill

Put your formula in first row in the entire column. Select whole column and use Fill > Down column.

Fill Down

As you see you copied formula to the every cell in the column. Also below 12 row where don't have any neighbors in column D.

Fill Down Entire Column

You can also copy entire row the same way. Use Fill > Right then instead Fill > Down

Further reading: 
How to add text in formula?
Monthly installment formula
Sumif formula