Use the below grille size calculator to find the grille area needed based on the airflow requirement, face velocity and the free area of the grille. The calculator starts with the default face velocity and free area. Enter the airflow and grille width to calculate the required grille area and grille height.
How to Use:
- Enter the airflow
- Click Calculate
Grille Width and Grille Height are the grille size result. For example, if the grille width is 10 and the grille height is 16, the grille size is 20×16 inches.
To check other grille sizes, change the Grille Width and click Calculate again.
Grille Diameter: If you want to use round grille instead, this calculator also show you the grille diameter needed to meet the required grille area.
Caution: The Grille Free Area is based on average value. It increase/decrease proportionally with the grille size. Therefore, I strongly suggest you read my Return Air Grille Sizing Guide to make sure you are using the right value for the calculation.
Important Note: This calculator is provided for convenience and informational purposes. The result should not be taken as absolute and the actual performance is not guaranteed. If you have doubt, I strongly encourage you seek my advice or any other HVAC professionals you trust.