CFM Airflow Calculator
FREE HVAC TOOL
CFM / Airflow Calculator
Estimate room airflow from room volume and air changes per hour (ACH).
Room dimensions
Required airflow
EstimateAirflow—CFM
Metric airflow—L/s
Metric airflow—m³/h
Room volume: —
This is a volume-and-ACH estimate, not a code-compliance or HVAC equipment-sizing determination.
How to use the calculator
Choose US / Imperial or Metric units, enter the room's length, width, ceiling height, and target ACH. The airflow estimate updates automatically.
Assumptions and limitations
The calculation assumes a rectangular room with uniform ceiling height. ACH is a user-selected target; appropriate ventilation depends on occupancy, use, applicable standards, and system design. The result does not account for duct losses, filter pressure drop, or fan performance.
