ACH Ventilation Calculator
Air changes per hour (ACH) from room size and airflow, and the airflow needed to reach a target ACH.
Inputs
m
m
m
m³/h
1/h
Results
- Air changes per hour
- 4.94 ACH
- Room volume
- 81 m³
- Airflow for target ACH
- 486 m³/h
- Airflow for target ACH
- 286 CFM
Formula
ACH = Airflow (m³/h) ÷ Room volume (m³)
Required airflow = Target ACH × Volume
1 CFM = 1.699 m³/h
Assumptions & limits
- Assumes perfect mixing; real effectiveness depends on diffuser layout.
- Typical targets: offices 4–6, classrooms 5–7, kitchens 15–30.
Worked example
Volume 81 m³; 400 ÷ 81 = 4.94 ACH; 6 ACH needs 486 m³/h (286 CFM).