Office.com/Setup - How to Create Calculated Fields and Totals Rows
Office.com/Setup - When you create a calculated field, you are adding a new field in which every row contains a calculation involving other numerical fields in that row. To do this, you must enter a mathematical expression, which is made up of field names in your table and mathematical symbols. You don’t need to know too much about math or expression building to create a useful calculated field. In fact, you can write robust expressions using only grade-school math. For instance, you could:
•Use + to find the sum of the contents of two fields or to add a constant value (such as + 2 or + 5)
to a field
•Use * to multiply the contents of two fields or to multiple fields by a constant value
•Use – to subtract one field from another or to subtract a constant value from a field
In our example, we will use a table containing the orders from one month. The table contains items listed by sales unit—single, half-dozen, and dozen. One column lets us know the number sold of each sales unit. Another lets us know the actual numerical value of each of these units. For instance, in the top row, you can see that two dozen fudge brownies have been sold and that one dozen equals 12 brownies.