According to Sizes.com, a 52-by-70-inch oval tablecloth fits a 22-by-40-inch oval table, leaving a 15-inch overhang around the edge of the table. The same tablecloth fits a 34-by-52-inch oval table with a 9-inch overhang, or a 40-by-58-inch oval table with a 6-inch overhang.
Sizes.com recommends a tablecloth overhang of 15 inches for a formal dinner and 9 inches for everyday dinners. If the overhang is just a few inches, the table looks a bit peculiar.
An oval tablecloth can dress a rectangular table, but the tablecloth overhangs the table by a different distance at the edges than it does at the corners. For a 15-inch maximum overhang of a 52-by-70-inch oval tablecloth, the largest rectangular table measures 22 by 40 inches.