When restaurant seating capacity and usable space disagree

Forty chairs on a patio look like forty seats. Then the first hot Saturday arrives, and the corner in full sun, the table by the door and the pair wedged against the planter stay empty. The number you can actually serve is closer to thirty.

Indoors the same gap hides better. Seating capacity gets used for three different numbers: the chairs on your drawing, the seats you can fill and serve on a busy night, and the occupancy your building is approved for. Furniture settles the first and shapes the second. The third belongs to your local building authority and a qualified reviewer, and no chair count stands in for that review.

What a chair takes with it

A metal ladder-back chair runs 17 inches across and 20 front to back. Tuck it 4 inches under a tabletop and 16 inches of chair still sticks out past the edge. A guest needs 18 to 24 inches behind that chair to pull it out and stand, and a service lane between chair backs runs about 36 inches. Everything else in a floor plan is addition.

Three distances fall out of those figures. From a table edge to a wall, count 34 inches at the tightest: 16 plus 18. From one table edge to the next, when two chair backs share 18 inches, count 50. Where a server walks between them, count 68: 16, a 36-inch lane, and 16 again.

One wall, two answers

Take a 24-foot wall, which is 288 inches, and 36-inch square four-tops. At the tightest, three tables use 34, 36, 50, 36, 50, 36, and 34 inches in a row, a total of 276. They fit with 12 inches to spare, so the wall seats 12.

Now let staff walk between the tables. Each gap becomes 68 inches, and three tables need 312, which is 26 feet. On a 24-foot wall only two fit: 34 plus 36 plus 68 plus 36 plus 34 is 208 inches, with 80 left over. The wall seats eight. Four seats disappeared into a lane.

The rule of thumb: when staff walk between them, a wall needs 8 feet 8 inches for every four-top. When nobody does, it needs 7 feet 2 inches for each, plus 18 inches in all.

Those 80 spare inches are not wasted. They are too short for another table and about right for a server station, a stack of high chairs, or a bench for guests who are waiting. Usable space is what remains once every seat has its room, and a good plan names what each leftover strip does. The common mistake is to divide the room's square feet by a seats-per-foot figure and order to that number. Rooms come in whole tables, so repeat the wall exercise across the other dimension and the leftovers multiply. The division overshoots what a tape measure finds.

Count tables, then chairs

Guests arrive in parties, not in chairs.

Picture a room of ten four-tops, 40 seats on the drawing. The 7 PM book holds twelve parties: seven pairs, three threes, and two fours, 31 guests in all. Ten tables seat ten parties, so two pairs wait. That leaves 27 guests in 40 chairs, a little over two thirds, with 13 empty seats nobody can fill. The room is full and the drawing says it is not.

More chairs wouldn't fix that. Tables sized to the parties would. Two guests fit a 30-inch square with their plates, and four fit a 36-inch square. A few tables for two near the window, tops that join for bigger parties, or a counter for singles and pairs all raise the number of parties the room holds at once. A folding metal table with a base offers a 30-inch round or square top and lists indoor and patio use. One table can work the dining room in January and the patio in June.

Our small restaurant table mix guide works out how many of each. Whether the twos should be square or round is a separate call, covered in round versus square tables.

Benches count by the inch

A bench has no chair arms to count, so you count inches. At 24 inches of table edge per diner, a 48-inch bench seats two, a 60-inch bench seats two with 12 inches to spare, and a 72-inch bench seats three. At the tightest, 18 inches a diner, the 60-inch bench seats three.

Eight booths built from a set of two wood benches with a solid wood table show the swing. The set lists bench lengths of 48, 60, and 72 inches, with a single bench 23 3/4 inches deep. Give each booth two 60-inch benches and you have 16 benches: 32 seats if you count two per bench, 48 if you count three. The furniture is identical and the answers are 16 seats apart, so choose the count you can defend on a Saturday and write it down. The booth collection shows what else comes in long runs.

The patio count has a clock

Outside, capacity also has a calendar. Chairs count in July and sit stacked under covers in January, and within a July day the west rail counts at noon and drops out at four. Our piece on restaurant patio furniture in direct sun shows how to find those seats.

Write two numbers in your patio plan instead of one: the seats you would sell at lunch and the seats you would sell on the late shift. A patio with 56 chairs, 20 of them in full sun at 4 PM, serves 36 at that hour, whatever the drawing says.

The third number is not furniture

Accessible seating and approved occupancy belong in the count from the first drawing. The figures below come from the 2010 ADA standards and are general guidance. For dining seating, section 226.1 sets a minimum of 5 percent at accessible surfaces. The route to those seats has to run 36 inches wide at a minimum (section 403.5.1). Section 902.3 wants the dining surface no lower than 28 inches and no higher than 34 from the floor. Beneath the top, section 306 asks for a knee pocket 19 inches deep, 30 inches wide, and 27 inches tall. Add a 30 by 48 inch patch of clear floor to pull up to.

In a 40-seat room, 5 percent comes to 2 seats. Your local code and the current edition of the standard have the final word, and your project may fall under more. Occupancy is a separate number again. Your local building authority sets it for the space, and a qualified reviewer works it out from the building, the exits, and the use. The room drawing on our planning page takes your width and depth in inches and tells you how many pieces fit, which settles the first number and leaves the third to the reviewer.

Tape the floor before you order a chair

Mark the plan on the floor first. Painter's tape works: outline each table, then its chairs 16 inches past the edge, then the lanes at 36 inches.

The walk-through comes next. Carry a tray of full water glasses down the lane. Sit someone in the end chair and ask them to stand up while a server passes behind. Park the stack of high chairs where it will live. Whatever bumps has to move. It takes two people and a roll of tape, and it shows you what the drawing hides.

Three numbers go on one line at the top of your plan: chairs drawn, seats usable, occupancy approved. Order from the second, and take the third to your reviewer before the furniture ships.