Hallo Binärbaum,
mit der
Mysql function
show table status kannst du dies rausfinden.
Data_free ist der Wert den du suchst
show table status from DATABASE like TABLE
[Name] => content
[Type] => MyISAM
[Row_format] => Dynamic
[Rows] => 5
[Avg_row_length] => 1400
[Data_length] => 18804
[Max_data_length] => 4294967295
[Index_length] => 8192
[Data_free] => 11804
[Auto_increment] => 17
[Create_time] => 2006-08-14 00:23:49
[Update_time] => 2006-08-23 17:08:20
[Check_time] =>
[Create_options] =>
[Comment] =>