Hello, To use the subtotal 1. Sort the data to subtotal 2. In the Outline group of the Data tab, click on Subtotal 3. In the Subtotal box, click the At each change in dropdown and select the column to subtotal on 4. Select the function from the use function dropdown 5. In the Add subtotal to dropdown, check the box where you want the subtotal to appear 6. Click OK. Note, Subtotal doesn't work when data is stored in Excel Table. Kindly let me know if this help.
You can't use subtotals in an "Excel Table". Convert your table to a normal data range (DATA, Table tools, Convert to range). Then the subtotal option will be available again in both the DATA menu and ribbon.