Use our CFM calculators and charts to determine how many vents you need for your project.

AV Diameters

Enter the length and width (in feet) or total square footage of your building in the fields below to determine how many vents are required based on the 1/150 or 1/300 Rule. This calculator is for the EXHAUST HALF ONLY. If an intake ventilator is needed, just double the amount of vents. For example, if 2 AV-14 are needed and inlet vents are needed, then an additional 2 PV-14 vents would be required

PV Diameters

UV Diameters

AF Diameters