International Sign Association (ISA)
1001 North Fairfax Street
Alexandria, VA 22314
Very few municipal codes regulate the actual face area of signs. Instead, they often regulate an approximation of the face area of signs. This happens for several reasons; the most commonly cited is ease of administration within the permit approval process.
The impact of this choice is that the area stated on a sign permit can differ from the measurements of the installed sign. Depending on the specific formula used to approximate the sign area calculation, the penalty can be more than 60 percent.
ISA supports the use of a measurement formula that measures the actual area of a sign. If an approximation formula is used, it should closely match the actual measurements for signs of any shape.