Do any of the following:
Total the numbers in a row or column
If the cell you selected is at the right end of a row of numbers, Word proposes the formula =SUM(LEFT). Click OK if this is correct.
Notes
Perform other calculations in a table
Do not delete the equal sign. If you deleted the equal sign, reinsert it.
To reference the contents of a table cell, type the cell references in the parentheses in the formula. For instance, to add the numbers in cells A1 and B4, the formula would read =SUM(a1,b4)
Note Word inserts the result of the calculation as a field in the cell you selected. If you change the values in the referenced cells, you can update the calculation by selecting the field and then pressing F9.
Note Microsoft Word table calculations must be manually recalculated. Consider using Microsoft Excel to perform complex calculations.