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Duct equivalent diameters and properties will include CFM, inches, and water gauge. As measurements are entered into Eastern Sheet Metal’s Rectangle to Round Duct Calculator app, the equivalent round diameter, air velocity, friction rate, and its total friction are calculated in seconds.

Enter Input Data for the following:

• a = length of one side of rectangular duct (in.)

• b = length of adjacent side of rectangular duct (in.)

• Q = volume flow rate (cfm)

• L = length of duct (ft.)

**Output:**

• D = equivalent round diameter (in.)

• V = air velocity (ft./min.)

• FR = friction rate (in. w.g./100 ft.)

• TF = total friction (in. w.g.)

Output delivers calculated and nominal outcomes

**To calculate oval to round**

Enter Input data for the following:

• aminor = minor dimension of flat oval duct (in.)

• amajor = major dimension of flat oval duct (in.)

• Q = volume flow rate (cfm)

• L = length of duct (ft.)

**Output:**

• D = equivalent round diameter (in.)

• V = air velocity (ft./min.)

• FR = friction rate (in. w.g./100 ft.)

• TF = total friction (in. w.g.)

Output delivers calculated and nominal outcomes

**To calculate rectangular to oval**

Enter Input data for the following:

• a = length of one side of rectangular duct (in.)

• b = length of adjacent side of rectangular duct (in.)

• aminor = minor dimension of flat oval duct (in.)