1. Select a cell in the PivotTable report.
2. Select Insert -> PivotTable (in Tables Group) -> PivotTable Tools -> Options -> Formula (in Tools Group) -> Formulas -> Calculated Field.
3. In the Insert Calculated Field dialog box, type the formula name in the Name box.
4. In the Fields list box, select the first field name to insert into the Formula text box, and click Insert Field. The field name is copied into the Formula box.
5. Type the divider symbol: / (in this example), repeat step 4 to insert the second field into the formula, and then click OK.
6. To format the new calculated field, select a cell in the new calculated field, right click and select Value Field Settings -> Number Format button.