The seating capacity for basketball at the Thomas and Mack Center is 18,776.
the seating capacity is 19,153 seats in the staidem
The Amway Center has a seating capacity of 18,846 for NBA games and 20,000 for NCAA basketball games.
For a basketball game there is 19309 seats
22,700
according to the website...27,000
the seating is 9,000 for family and friends and 11,000 for fans that have tickets
The Center accommodates 18,600 attendees for basketball, 17,800 for hockey and up to 20,000 for concerts.source: http://www.bradleycenter.com/seating/index.asp
According to the Toyota Center's website (http://www.houstontoyotacenter.com/about/atozguide.php#S), seating capacity is 18,300 for basketball.
The seating capacity of the MassMutual Center changes depending on the event being held. It can hold 6,800+ people for a hockey game, 7500+ for a basketball game, and over 8,500 people for concerts.
It would depend on which sport / event is playing. Link to the seating charts below.
FedExField has a seating capacity of 82,000 people.