Duct Sizing Calculator
Size round and rectangular ducts from airflow using the equal-friction or velocity method.
Free · no sign-in requiredPurpose
Size round and rectangular ducts from airflow using the equal-friction or velocity method.
Inputs required
Airflow, design friction rate or velocity, and aspect ratio for rectangular ducts.
Standards followed
ASHRAE Fundamentals duct design and SMACNA practice.
Free to use. No sign-in needed.
Open the Duct Sizing CalculatorEngineering reference & methodology
What you get
Duct size, air velocity, friction loss and equivalent round diameter.
Results are preliminary design guidance. Verify every value against the edition of each standard adopted by your project or authority having jurisdiction, and against manufacturer performance data, before using it in design or procurement.
Psychrometrics, cooling loads, duct & pipe sizing, pumps, cleanrooms, electrical design and PDF reports.