Air Changes per Hour (ACH) Calculator

Air Changes per Hour (ACH & ACPH) Calculator Tool

Use our free online Air Changes per Hour (ACH & ACPH) Calculator to determine the air changes per hour (ACH) and ventilation rate of your space based on its dimensions, your air filtration device, and other relevant factors. Understanding your ACH or ACPH—commonly referred to as the “air exchange rate” or “air change rate”—allows you to calculate how many times the air within a given space is replaced, removed, or exchanged with fresh, filtered air per hour.

Air Changes per Hour (ACH) Calculator

Room Dimensions

Air Filtration Device

Results:

  • Room Volume: N/A ft³
  • Total Airflow: N/A CFM
  • Air Changes per Hour (ACH): N/A
  • Air Changes per Minute (ACM): N/A

Air Changes per Hour Formula

The Air Changes per Hour Formula or ACH formula is used to determine how many times the air within a space is replaced each hour. The formula for ACH considers the following metrics:

ACH = Air Changes per Hour

CFM = Cubic Feet per Minute (airflow rate of the ventilation system)

V = Volume of the room (in cubic feet)

60 = Conversion factor (minutes to hours)