Is there a way to have submissions add together automatically?

Or will I always have to do it manually using excel?

I'm not sure if I understand the question. If you want to have the entire submission in single file, you can have it as an Excel or CSV.

https://www.jotform.com/help/73-How-to-Download-Form-Submissions-as-Excel-CSV-PDF

If you want to automatically update the file for new submissions, you may consider our Google Spreadsheet integration.

https://www.jotform.com/help/228-How-to-Integrate-Form-with-Google-Spreadsheet

Note that we also have the following reporting options:

https://www.jotform.com/help/209-How-to-create-an-HTML-Table-Listing-Report

https://www.jotform.com/help/105-How-to-create-a-Grid-Listing-report 

I hope that helps.