ACH Ventilation Calculator
Calculate Air Changes per Hour (ACH) or determine the required CFM for a room.
Room Dimensions
Ventilation Variables
Leave one field blank to solve for it.
ASHRAE Ventilation Standards
Air Changes per Hour (ACH) represents how many times the total volume of air within a space is completely replaced in one hour. Proper ACH is mandated by ASHRAE standards for indoor air quality and infection control.
Calculate ACH from CFM:
$$ ACH = \frac{CFM \times 60}{\text{Room Volume } (ft^3)} $$
Calculate required CFM: $$ CFM = \frac{\text{Room Volume } (ft^3) \times ACH}{60} $$
Calculate required CFM: $$ CFM = \frac{\text{Room Volume } (ft^3) \times ACH}{60} $$
Common ACH Guidelines
- Offices & Classrooms: 3 to 6 ACH
- Commercial Kitchens: 15 to 20 ACH
- Hospital Operating Rooms: 20+ ACH