Converting an area to square feet would seem simple, unless the area is spread over a form with height, width and depth. Then, you have to convert the outside of that form, its perimeter and length into a workable flat surface and convert the area of that flat surface to square feet. It's a simple enough process as long as you remember the formula.
Things You'll Need
- Measuring tape
Measure one side of the duct from top to bottom, then measure the bottom of the duct from left to right, if the duct is square or rectangular. Use a measuring tape that measures in inches. Use the calculator to add these two measurements together and multiply by two. This tells you the length of the perimeter of the duct.
Measure the length of the duct--in inches--and multiply that measurement by the length of the perimeter of the duct. This will tell you how many square inches are in the duct area. Divide this result by 144, the number of square inches in a square foot. This will tell you how many square feet are in the duct area.
Measure the distance across the duct, in inches, then multiply by 3.14159 if the duct is circular to find its circumference, in inches. Then, measure the length of the duct--in inches--and multiply by the circumference. This is the number of square inches in the duct area. Divide by 144 to determine how many square feet are in the duct area.
How to Calculate Cubic Feet in an Air Duct
Ductwork length is critical in HVAC systems because ductwork that is too long can significantly reduce the efficiency of the HVAC unit....
Measuring Static Pressure Drop in HVAC Ducts
Heating, ventilation, and air conditioning ducts, or HVAC ducts, channel the flow of climate controlled air throughout buildings with centralized systems. Return...
How to Calculate Duct Volume
A duct--which resembles a long, flexible tube--is used in a heating, ventilation, and air conditioning system to deliver and remove ventilation, supply,...
How to Calculate an Air Conditioning Duct
Installing the right size HVAC duct is crucial for an efficient HVAC system. Ducts that are sized too large will have too...
How to Calculate SCFM in an Air System
Standard cubic feet of air per minute (SCFM) is used to measure air flow in a ventilation system, and requires rigid standards...
How to Measure Ductwork
Ductwork is found in square, rectangular or round form. You may have occasion to measure the size of the ductwork. If you...
How to Calculate Duct Airflow
All heating, air conditioning and ventilation systems use ducting to deliver air from the heating or AC units to the desired locations...
How to Convert a Round Duct to Rectangular
In your home heating/air conditioning system, you have ductwork to push air through your home. Round ducting is often found -- it...