The standing room capacity of a space is a measure of how many people can safely and comfortably occupy it while standing. This is a useful measure for venues that people typically attend in a standing position, such as concerts, bars, and nightclubs. Standing room capacity is similar to the maximum occupancy, which is the absolute maximum number of people that can safely occupy a room. Maximum occupancy is determined by a fire marshal, and the rules for determining it differ between municipalities. Thankfully, it is possible to calculate a relatively good approximation of SRC using a few basic measures.
Calculate the total area of the room. If the room is square or rectangular this is fairly easy; simply use a tape measure to measure the length and width of the space and multiply them together. If the room is any other regular geometric shape, it is nearly as easy: input the basic measurements of the room into the appropriate geometric formula to find the area.
Calculate the area of any places that cannot be occupied by standing people. Examples include stage areas, bars, seating areas, and tables. Add about 10-15% to this figure to account for people pushing their chairs out when they sit around tables or extending their legs when seated on couches and benches. Subtract this figure from the total usable area of the room to find the total available standing room.
Decide how much room you want to assign to each standing person. If you are running a concert, you will likely need less room per person than if you are the proprietor of a bar. Figure on a minimum of 9 square feet per person, corresponding to a 3-ft. by 3-ft. space. Remember that you can't pack human beings like sardines; there will need to be room between them so that people can enter, leave, and move about the room to get to rest rooms and seating areas. A more common figure is 36 square feet per person.
Divide the total available standing room by the area you have allotted for each person to find the standing room capacity of the space.
If the room is irregular in shape, calculating its area might be more difficult. One possible approach is the divide the room as best as possible into a set of easily-delineated geometric shapes that you can apply the basic area formulas to. For instance, a room might be rectangular at one end but have a semicircular area at the other. In this case you would measure the length and base of the rectangular part of the room to find its area, then measure the radius of the semicircular part, use it to calculate the area of a circle with that radius, divide by two (because it is only half a circle), and add the result to the area of the rectangular part to find the total area of the room.
The number of people in the room must never under any circumstances exceed the fire marshal-determined maximum occupancy.