Duct Sizing Calculator

Calculate the required duct diameter for a given airflow rate and maximum velocity.

L/s
m/s

Required Circular Duct Diameter

252 mm

Minimum Duct Area50,000 mm^2
Actual Velocity at Selected Size6.0 m/s

Required Circular Duct Diameter vs Airflow Rate (Q)

Vedi formula →

Formula

## HVAC Duct Sizing Duct size is determined by the airflow requirement and an acceptable air velocity. ### Formula **A = Q / V** (required area) **D = sqrt(4Q / (pi V))** (circular duct diameter) where Q is airflow in m^3/s and V is maximum velocity in m/s. Higher velocity means smaller ducts but more noise and pressure drop.

Esempio Risolto

300 L/s airflow with 6 m/s maximum velocity.

  1. 01Q = 300 L/s = 0.30 m^3/s
  2. 02A = 0.30 / 6 = 0.05 m^2 = 50,000 mm^2
  3. 03D = sqrt(4 x 0.30 / (pi x 6)) x 1000 = sqrt(0.0637) x 1000 = 252 mm
  4. 04Round up to next standard size: 250 or 300 mm duct.