CFM Anemometer - Calculating Area

Air volume is calculated by measuring the air velocity and comparing it to the area that the air is moving through. This is most common in HVAC applications. As such, it is necessary to enter the area of the enclosure (duct, valve, etc.) into the CFM Anemometer prior to taking the reading so that it calculates CFM properly. To do so, follow these instructions:

1. First determine the surface area of the opening using the area formula for the shape of the opening: Circle - A = pi x radius ^2; Rectangle - A = length x width; Triangle - A = 0.5 x base x height.

2. Now that you know the surface area of the opening, you need to convert the number to square feet. Most often your answer will be in square inches. So, to convert sq. in. to sq. ft. you divide sq. in. by 144 (there are 144 sq. in. in 1 sq. ft) and you will have your answer. This is the number you enter into the CFM Anemometer.