Airflow Calculator
Calculate duct airflow, room ventilation airflow, or air velocity using practical HVAC formulas, clean results, and a one-page PDF export.
Enter your values
Choose the method that matches the values you already have.
Use the clear inside duct diameter.
Use internal width only.
Use internal height only.
Use the average measured or design air velocity.
Measure the usable inside length.
Measure the usable inside width.
Use the actual finished ceiling height.
ACH means how many times the room air is replaced in one hour.
Use the clear inside duct diameter.
Use internal width only.
Use internal height only.
Enter the airflow you already know.
Use the unit that matches your source value.
Results
The main result appears first, followed by practical converted values and input details.
Enter your values, then click Calculate.
Note: This tool gives practical airflow calculations for common ventilation and duct sizing checks. Final system design should still match your project standard, local code, and actual field conditions.