How to Size an Air Purifier for Your Home: Calculate the Size of an Air Filter Needed

If you are wondering what size or how "strong" of an air purifier you need, these two calculators will help.

To properly size an air purifier or filter for your home or room, the main value you are looking for on an air purifier's specs is how much air it moves. This will be provided by the company as the CFM (Cubic ft/Minute) value. Think of this as the fan size.

I have two posts on air purifiers - one on PCO types and one on HEPA/Carbon to help you compare models once you have sized them with these charts. If you need help choosing the right air purifier for your needs and sizing them to your space, you can contact me here for a one-on-one consult.

The First Calculator: Calculate What Size Air Purifier you Need 


In the first calculator you will find out what CFM value you need for your room size. You need to add your desired or ideal Air Exchange Per Hour (ACH). This is how many times you want the unit to overturn (and filter) the air in the room per hour.

This calculator will tell you what (minimum) CFM value you are looking for and then below is a list of air filters that meet that requirement.

Air Purifier to Choose based on Result of Required CFM from the Calculator (Note if the required CFM is over 400 you will need more than one unit, I recommend calculating each room at a time, not the whole house). 


PCO Models Best for Mould Reduction:

Airocide CFM 14
Molekule CFM 80
GermGuardian AC4825 CFM 125
Vornado PCO300 CFM 145
Vornado PC0500 CFM 184

Here is the Post with Detailed Comparison of These Models

High Carbon (and other Sorbant Material) Best for High Offgassing: 

Amaircare 3000 225 CFM
Austin Air Healthmate Plus CFM 250
EnviroKlenz CFM 250
IQ Air Multigas CFM 300
E.L. Foust 400 Series CFM 380
AllerAir AirMedic Pro 5 Ultra CFM 400
Airpura C600-DLX 440 CFM

Here is the Post with Detailed Comparison of these Models

The Second Calculator: Calculate How Effective Your Air Purifier is in Your Space (How Much Air is it Cleaning)


Below, the second calculator can tell you how many air exchanges per hour you are getting from an air purifier you already have, or one you are looking to buy, based on the size of your room.

Most experts recommend a minimum of 4 ACH. ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) recommends a minimum of 4 ACH for patient rooms in hospitals, 5 for intensive care units and 25 for operating rooms.

Hopefully these two calculators helped you find out your ACH to CFM calculation and your CFM to ACH calculation.





Corinne Segura is a Building Biologist with 5 years of experience helping others create healthy homes.


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