How To Add A Summary Formula
Follow the steps below to add a summary formula for columns in your reports.
Step 1: Locate and click on the “Reports” tab on the left-hand side.
Step 2: Click on the report you would like to edit or create a new report.
Step 3: Click "Edit".
Step 4: Click on the drop-down arrow next to “Add Columns”.
Step 5: Click "Add Row-Level Formula".
Step 6: You will now see a list of fields and functions to create your formula. All fields on the object should be visible inside this summary action. Choose the fields and functions necessary to accomplish your summary goal.