At 2.5 square feet per person, which is somewhat standard for the room taken up by one standing person, then you could fit 18,000 people into a football field that measures 100yds x 50yds. They would not be happy, but they could fit.
The seating capacity of FedEx Field for football is 91,704.
It has a capacity of 10,104.
Faurot Field has a seating capacity of 71,168 people.
Around 10,000+
Frank Howard Field at Memorial Stadium has a seating capacity of 81,500 people.
EverBank Field has a seating capacity of 76,867 people.
The seating capacity of Memorial Stadium, Lincoln, Nebraska is 86,047 people. The seating capacity of Frank Howard Field at Clemson Memorial Stadium, Clemson, SC is 81,500 people. The seating capacity of Memorial Stadium, Champaign, Illinois is 60,670 people. The seating capacity of Memorial Stadium (Baltimore) was 53,371 (1991). The stadium was closed in 1997 and demolished in 2002.
The capacity of Ryan Field Stadium is 47,130. It is the stadium used to host football games for Northwestern University Wildcats in Evanston, Illinois.
The stadium's seating capacity is approximately 65,000 for Cardinals games and is expandable to over 73,000 for megaevents like the Super Bowl and Fiesta Bowl.
Soldier Field has a seating capacity of 61,500 people.
Invesco Field at Mile High seats 76,125 for football games.
Invesco Fields seating capacity for a football game is 76,125. http://www.stadiumsofnfl.com/afc/InvescoField.htm