Air Changes Per Hour Calculator from CADR & Room Size

Air Changes per Hour (ACH or ACPH) of an air purifier determines how many times the machine can exchange the whole volumetric air from a specific sized room in an hour. For example, an air purifier can make 2 ACH in a 300 sq ft room, which means it takes 30 minutes to clean.

Find your Air Changes Per Hour (ACH) using the calculator below.

Check out our top picks >>> The 7 Best High CADR Air Purifier.

Air Changes per Hour Calculator:

Enter your air purifier’s Clean Air Delivery Rate (CADR) either in cubic feet per minute (cfm) or cubic meter per hour (m³/h), and your room dimensions to calculate the Air Changes per Hour (ACH) of your air purifier.

Here is the formula:

Air Changes per Hour = [(CADR in cfm x 60) / (L x W x H)] per hour