You can add Formulas to Tables in Microsoft Word with relative ease. To learn how to insert Formula in Word Table, read this article.

Review the Formula Format table in the graphic below for the correct commands that tell Word which direction to calculate (these go inside the parentheses).

To create a formula, click inside the cell where you want the product to appear and go to the "Layout" tab of the Word Ribbon. Click the "Formula" icon and enter "=PRODUCT" in the "Formula" field.