How do you meansure for a table cloth?

I don't understand how you measure for a table cloth! Am I supposed to add inches past each edge for over-hang? When I order, do I use the exact numbers matching them exactly or nearly to the sizes they show for the tablecloth measurement? Thank you.How do you meansure for a table cloth?
A table cloth should hang 6-8 inches on all sides if your chairs have arms, 12 inches if they don't.How do you meansure for a table cloth?
I don't completely get it either. But this is what I do and it works.First measure the length and width of your table. The packaging should say what size table the table cloth works for,you don't need to add inches to the measurement. If your ordering it,some where on the page should say what size table it works for. It might be better to go to the store and get it and make sure you can take it back just in case it doesn't fit right. Good luck P.s. That 6-8 inches over hang doesn't always work if you have an odd shaped table.