How the size is worked out
Measure the tabletop: length and width for a rectangle or oval, one side for a square, the diameter for a round table. If the table extends, measure it the way you will use the cloth. The cloth is the table plus twice the drop in each direction, because the drop hangs on both sides.
Drop is the distance the cloth hangs below the edge. US guides call 6–8 inches (15–20 cm) normal for everyday meals and 10–15 inches for formal ones; European makers start from 20–30 cm. A floor-length cloth drops the full table height, less a small gap so it does not drag. Before deciding, hold a tape beside a chair: a long drop can rest on knees and chair arms.
Ready-made sizes rarely match exactly, so the table shows how each common US size would hang on your table. Pick the next size up when in doubt, and allow an inch or two for cotton or linen that may shrink in the wash. A square cloth on a round table, or a rectangular one on an oval table, hangs lower at the corners.
Example: a 180 × 90 cm table with a 25 cm drop needs a cloth of 230 × 140 cm; anything from 220 × 130 to 240 × 150 cm keeps the drop within 20–30 cm.