How do you find cfm in duct?

To find cubic feet per minute (CFM) in a duct, you can use the formula: CFM = Air Velocity (feet per minute) × Duct Area (square feet). Measure the air velocity using an anemometer and calculate the duct area by multiplying the width and height for rectangular ducts or using the formula for the area of a circle (π × radius²) for round ducts. Multiply these two values to get the CFM. Alternatively, you can use duct flow measurement devices or tools for an accurate reading.