If you have 300 passengers on a flight, how much cargo does that equal.
This simple answer is that it varies depending on the airline, season, ect. In American Airline’s case for example, “ All checked bags must adhere to a max weight of 23kg for Economy & Premium Economy; 32kg for Business & First Class fares […]”, according to this article. There are of course added fees for extra baggage.
So times that by the amount of passengers and you can get a rough estimate of how much baggage there would be.
1. “American Airlines Baggage Fees & Tips to Cover the Expenses” by UpgradedPoints.