The rule of thumb I always heard was to add the length and width together to get the desired diameter of the chandelier. So that would be 16.5 + 13 = 29.5" minimum diameter. If you post some pictures of your table and current choices, many folks will chime in to assist in chandelier selection.

Hello! I wish I could see a picture, they sound so pretty. I would definitely go with the 29"h x 27.5"w one. Two reasons why. 1. I would base it off the room size in this instance and the 27.5" one fits it perfectly. 2. The 39.3"w one may actually be in the way when people stand up at the table- they could hit their head. You should have about 4-6" on either side of the table for some head space. Good luck!

Thank you to both of you! Andrea, you make a great point about hitting your head. Here are the two chandelier pictures:

The 29' high x 27.5' one:

The 39.3"w one: