I am sure someone can chime in with actual guidelines regarding how much clearance you will want around the table/chairs.

When we were picking out a dining room set, it helped me to put painters tape on the floor with the table and chair dimensions to get a better feel for it. Since you aren't moved in yet, you could tape off the dimensions of your future dining room, and then tape off the dimensions of the table centered inside that. And then tape together a few pieces of paper for the chairs (whatever the chair seat dimensions are), which you can slide around. I am not sure if any of that makes sense. I know it isn't perfect, but if you are a visual person, it might help you picture the spacing better.

Subtract 36" from the inside the wall dimensions on each side of the table, or from any buffet on the walls. That is the size table that will fit after you account for aisles for people and chairs. Construction dimensions are not inside the wall dimensions. They are center of wall to center of wall, inside the wall. You have to subtract the wall thickness first.

You will need 24 inches all around the table in order to pull out the chairs. Ideally, you don't want the room to feel cramped or have guests not be able to enter and exit the table when others are seated.

Don't purchase a table until the room is finished.