Airflow cluster
Air Changes per Hour Calculator
Calculate ACH from measured or specified airflow.
How to use
Enter room dimensions and total airflow in CFM.
Formula
ACH = CFM × 60 ÷ room volume
Variables
CFM is flow; room volume is ft³; ACH is changes per hour.
Example
240 CFM in a 2,400 ft³ room equals 6 ACH.
Result interpretation
Measured supply, outside air, exhaust, and filtered recirculated airflow serve different purposes.
FAQ
Does ACH mean all air is perfectly replaced?
No. It is a volumetric rate, not a mixing guarantee.