When performing your calculations, remember that the formula to determine the circumference of a circle is C = d x π (pi, 3.14159) times the diameter. To calculate the number of settings for long tables, multiply the length of the table times two, divide the total by 30 inches and add two settings for the ends.
Using the above formula for finding the circumference of a circle, you can determine that a round table with a diameter of 48 inches can comfortably seat four or five people; a 54-inch table, six people; a 60-inch table, six people; and a 72-inch table, eight people. You wouldn't want a round table any larger than 6 feet because it would be too big for conversations to occur and there would be all that dead space in the middle.
When you use the formula for the number of settings per long table, you come up with the following results: A 40 x 72-inch table comfortably seats six guests; a 44 x 84-inch table, eight guests; a 48 x 96-inch table, either eight or ten guests if you squeeze in two at each end. Given the average size of dining rooms in today's homes, any table bigger than this would make getting into their seats impossible for guests.
Besides your personal taste and feeling that a round table is more inviting and more conducive to socializing, there are practical matters. For one thing, round tables are space savers. For another, you don't feel so cheek-to-jowl with your fellow diners, and maneuvering in and out of your seat is easier.
On the other hand, a long table seems more formal but can be informal if you're serving family style. If you opt for a long table, make certain that the width is in proportion with the length and can accommodate serving dishes and centerpieces. In social terms, people find conversing with the people on either side of them and across from the table more comfortable.