If you need to sum a column or row of numbers, let Excel for the web do the math for you. Select a cell next to the numbers you want to sum, click AutoSum on theHometab, press Enter, and you’re done.

Sum a row of a table in Word. If you want to sum a row of a table in a Word document, do as follow: Step 1. Place the cursor at the blank cell of the first row, then click layout > Formula, see screenshot:

Word can add! Seriously, if you're using Word and you need a few basic calculations, you don't have to insert an Excel sheet. You can use a Word table and let Word do the calculating.