For formal events, a tablecloth should have a 15-inch drop from the edge of the table to the bottom of the material. For casual dining, the drop doesn’t need to be as long so 6- to 8-inches of drop from the edge of the table to the bottom of the tablecloth is perfect. To figure the length of cloth you need, measure the length and width of your table, then add twice the desired drop (depending on whether it’s a formal or casual gathering) to each side’s dimension. For round tables, measure the diameter of the table then add twice the desired drop. For example, to fit a round table that’s 60-inches wide with a 15-inch drop, you’d need a 90-inch round tablecloth.