Just buy a tablecloth that is longer than 100 cm and wider than 60 cm. If you want to sag more, buy a tablecloth with 150 and 1 10. Want to droop less, buy a tablecloth with a width of 120 and 80.

If you want a corner of the tablecloth to hang down from the center of the table, the edge of the square tablecloth should be larger than 1 15, so buy a tablecloth with 120* 120.