Ventilation Airflow (m³/h & l/s) and Duct Diameter Calculator

Calculate required mechanical ventilation extraction airflow in m³/h and l/s and circular duct diameter for bathrooms, kitchens, offices and garages.

Room Area (m²)

Ceiling Height (Meters)

Room Type (Air Changes/h)

Max Duct Air Velocity

Required Airflow (m³/h)240 m³/h

Airflow in Liters/sec66.7 l/s

Standard Duct DiameterØ 150 mm

Actual Air Velocity3.77 m/s

Air Renewal Rate & Circular Duct Continuity Equations

Ventilation Standard (ASHRAE 62.1 / 62.2 & EN 16798): Keeping air velocity between 3.0 and 4.0 m/s in residential branch ducts prevents aerodynamic noise.

Airflow: Q (m³/h) = Area (m²) × Height (m) × Air Changes/hour (ACH)
Theoretical Duct Diameter (mm): D = 1000 × √((4 × (Q / 3600)) / (π × Velocity_m/s))

Minimum Regulatory Ventilation Rates by Room Type

Room / Space	Min Airflow (l/s)	Equivalent in m³/h	Typical Duct Diameter
Bathroom or restroom (per room)	15 l/s	54 m³/h (continuous minimum)	Ø 100 mm / Ø 125 mm
Kitchen (general background ventilation)	2 l/s per usable m²	7.2 m³/h per m²	Ø 125 mm
Kitchen range hood (direct extraction)	50 l/s	180 m³/h (regulatory minimum)	Ø 125 mm / Ø 150 mm
Enclosed parking garages (per car space)	120 l/s per parking space	432 m³/h per vehicle	Main collector duct

Frequently Asked Technical Questions (FAQ)

How do you calculate room ventilation airflow in m³/h?

Multiply room volume (Area m² × Height m) by required Air Changes per Hour (ACH: 6 to 12 ACH depending on room type).

How do you size duct diameter for quiet operation?

Keep air velocity between 3.0 and 4.0 m/s in residential ducts using D = √((4 × Q) / (π × v)) to prevent aerodynamic noise.