While there are many sizes of tables that may need covered, there are several sizes that are most common in venues. For rectangle tables, the question of what size linens you need directly relates to whether you want half or floor length linens.
If a half-length cloth is preferred, use a 60x120 cloth for either size; simply pleat the linen in the middle on the 6ft table.
Floor length for a 6 ft rectangle table is 90x132, and for an 8 ft rectangle is 90x156.
Some choose to use two 90-square linens and overlap them in the middle since many specialty items do not always come in every size and a 90-Square is the most common size.
Overlays may be placed on the diagonal (points touching the floor) or placed in the center of the table. Typically 90-Square linens are used for overlays on rectangle tables.
Half Length Linen
Floor Length Linen