Air conditioning tonnage per square foot is the ratio of the air conditioner's capacity divided by the square footage of the space it services. Experts typically use the opposite ratio of square footage per ton of air conditioning capacity.
In heating, venting and air conditioning terminology, one ton refers to 12,000 British thermal units per hour of cooling capacity. Determining how much many tons of cooling capacity a room requires can be difficult, but online calculators and charts can give users guidelines. Since square footage deals with surface area, structures with taller than average ceilings tend to need a greater tonnage per square foot. Similarly, homes with extra windows and other spots where the building is less insulated typically require a higher ratio.