Choosing the size of a tablecloth depends largely on the shape and size of the table, as well as your personal preference for the drape of the tablecloth. Here are the details:

Round Tables. For a round table, you can choose a round tablecloth that is the same as or slightly larger than the table's diameter, or you can choose a square tablecloth, which has a drape of about 15 to 30 centimeters on one side. For example, if the diameter of a round table is 90 centimeters, you can choose a round tablecloth with a diameter of 150 centimeters or a square tablecloth with a diameter of 150 x 150 centimeters.
Square or rectangular tables. For square or rectangular tables, the length and width of the table need to be measured. The size of the tablecloth should be the tabletop size plus the length of the drop edge on each side, which is usually between 15 and 35 centimeters. For example, if the table is 120 cm x 80 cm, you can choose a tablecloth that is 145 cm x 165 cm, with a drop edge of about 20 cm on each side.
Oval or other shaped tables. For oval or other shaped tables, it may be necessary to consult the merchant's customer service or professional advice to determine the right size.
Coffee tables. For coffee tables, as the typical height is between 45 and 50 centimeters, the tablecloth should be appropriately smaller, with a sag of about 15 centimeters all around. For example, a 60 cm x 120 cm coffee table can choose a 90 cm x 150 cm tablecloth.
It is important to note that the size of the tablecloth should also take into account the height of the table and personal preferences. For example, if you prefer a longer draped edge, you can choose a tablecloth with a slightly larger size.