It makes good business sense to put as many seats in a restaurant dining area as you can, provided patrons don’t feel crowded and uncomfortable. Before you calculate the seating capacity for the interior of a restaurant, check local fire codes. Your fire department probably sets safety standards covering things like maximum occupancy, number of exits and width of aisles between tables. The website for Selected Furniture, a manufacturer of commercial furniture for the hospitality industry, says the rule of thumb for most restaurants is that 60% of the total building space should be allotted to the dining room and 40% to the kitchen.

Define the Interior Space

The dining area of a restaurant typically consists of one or more rectangular spaces. Multiply the length of each rectangular section by its width to calculate the area in square feet. Add the section areas together to find the total floor space. Next, subtract the square footage taken up by wait stations and decorative features such as planters or interior fountains. If you have a bar, subtract a strip 3.5 feet wide multiplied by the length of the bar. The resulting square footage is the available seating area. According to Selected Furniture, "the traffic path between occupied chairs should be at least 18 inches wide," and you should leave four to five feet between tables.

Calculate Seating Capacity

Divide the available seating area by the square footage per customer. For fine dining, allow 18 to 20 square feet per customer, Selected Furniture suggests. A fast food restaurant needs about 11 to 14 square feet per person. Full-service establishments that are not fine dining should allocate 12 to 15 square feet. Add one bar stool for every 2 feet of bar length to find the total interior seating capacity of the restaurant.