TDM doesn’t offer such functionality for tables, you will have to write your own script that will estimate table sizes and write the value to the Size field automatically for you. You can have in your db design columns of various data types and when you define column in your database structure, there is no information about data, I mean when column is of certain datatype (blob) or is nullable for example, then it’s probably difficult to estimate table size. The Size field is there for you to manually specify estimated table size. Also, you can use your own units (kB, MB…).
To estimate database size you can follow instructions written here:
It’s a script that will calculate database size from values defined in Size field in your entities.