We usually have a minimum of 5 feet from the edge of the fire pit. 2 feet of space and 3 feet for a club style chair.
An area of about 15x15 is fine, especially if the outside diameter of the firepit is five ft.

When building in seating it is a good idea to leave about 2'-0" feet min to 2'-6" max of space between pit and bench. This is so that you can put your feet up on the edge of the pit and also leave enough room to walk around the pit.

We usually make the pit height 18 to 20 inches high. {{gwi:6937}}From outdoor fire places rings
{{gwi:18187}}From outdoor fire places rings