Calculate Round Duct Area to Square Feet

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Round ducts are a common type of duct used in HVAC systems. The duct area is a crucial parameter in determining the size of the ductwork, which in turn affects the system’s efficiency, air flow, and overall performance. The duct area is the total cross-sectional area of the duct, and it is usually expressed in square feet.

Here are the steps to Calculate Round Duct Area to Square Feet:

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Measure the Round Duct Diameter

The first step in calculating round duct area is to measure the diameter of the duct. The diameter is the distance across the duct at its widest point. It is important to measure the diameter accurately to ensure an accurate calculation.

Round Duct Area Formula

Once you have measured the diameter, the next step is to calculate the area of the duct. The formula to calculate the area of a round duct is πr², where r is the radius (half the diameter).

Convert the Round Duct Area to Square Feet

The final step is to convert the area from its current units to square feet. To do this, divide the area by 144, since there are 144 square inches in a square foot.

Let’s consider a few examples to illustrate the steps involved in calculating round duct area to square feet.

Example 1: 

Suppose we have a round duct with a diameter of 12 inches. To calculate the area, we first find the radius by dividing the diameter by 2, which is 6 inches. Next, we use the formula πr² to find the area, which is 113 square inches. Finally, we convert the area to square feet by dividing by 144, which is 0.78 square feet.

Example 2:

Suppose we have another round duct with a diameter of 8 inches. To calculate the area, we first find the radius by dividing the diameter by 2, which is 4 inches. Next, we use the formula πr² to find the area, which is 50.27 square inches. Finally, we convert the area to square feet by dividing by 144, which is 0.35 square feet.

Convert Round Duct Area to Square Feet

Duct Diameter (Inches) Duct Diameter (mm) Area Ft² Area m²
8 203 0.3491 0.032
10 254 0.5454 0.051
12 305 0.7854 0.073
14 356 1.069 0.099
16 406 1.396 0.130
18 457 1.767 0.290
20 508 2.182 0.203
22 559 2.640 0.245
24 609 3.142 0.292
26 660 3.687 0.342
28 711 4.276 0.397
30 762 4.900 0.455
32 813 5.585 0.519
34 864 6.305 0.586
36 914 7.069 0.657
38 965 7.876 0.732
40 1016 8.727 0.811
42 1067 9.62 0.894
44 1119 10.56 0.981
46 1168 11.54 1.072
48 1219 12.57 1.168
50 1270 13.67 1.270
52 1321 14.75 1.370
54 1372 15.90 1.477
56 1422 17.10 1.586
58 1473 18.35 1.705
60 1524 19.63 1.824

Calculating round duct area to square feet is an important step in determining the size of ductwork for HVAC systems. The process involves measuring the diameter of the duct, calculating the area, and converting the area to square feet. With the right tools and a clear understanding of the formula, you can easily calculate round duct area and ensure your HVAC system is operating efficiently. It is important to note that the accuracy of the calculation depends on the accuracy of the measurement of the diameter.

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