Airflow, Ductwork & Ventilation Calculators

Calculate air velocity in FPM and m/s in round or rectangular ducts from airflow and duct size.

Size a round duct for a target velocity from airflow, with metric output and nearest standard size.

Convert rectangular duct dimensions to equivalent round diameter for equal friction (Huebscher equation).

Estimate friction loss per 100 ft and for a duct run from airflow and round duct diameter.

Calculate air changes per hour from airflow and room volume.

Calculate required ventilation airflow in CFM and L/s from a target ACH and room volume.

Calculate airflow per ton of cooling and L/s per kW.

Calculate total external static pressure from supply and return readings and compare with the blower's rated static.

Predict new airflow, static pressure and fan power after a speed change using the fan affinity laws.

Calculate fan brake horsepower from airflow, total pressure and fan efficiency.

Calculate the outside surface area of round or rectangular duct for insulation and sheet metal estimates.