HEPA Room ACH Calculator
Number of HEPA units for a target ACH.
Enter your values
ⓘ Live results
Results
- Total airflow needed
- 450 CFM
- HEPA units required
- 2
- Room volume
- 4,500 cu ft
Quick answer
The number of HEPA units needed equals the target air changes per hour times room volume, divided by 60 and the unit's rated CFM.
Units = (ACH x volume) / (60 x unit CFM)
How to use the HEPA Room ACH Calculator
- 1Compute the room volume from its floor area and ceiling height.
- 2Multiply by the target air changes per hour and divide by 60.
- 3Divide the total CFM required by each unit's rated CFM and round up.
Worked example
Using the values the calculator loads with:
Inputs
- Room area500 sq ft
- Ceiling height9 ft
- Target air changes6 ACH
- CFM per HEPA unit300 CFM
Results
- Total airflow needed450 CFM
- HEPA units required2
- Room volume4,500 cu ft
Frequently asked questions
What ACH should I target for infection control?
CDC guidance for temporary isolation spaces commonly cites 5+ equivalent ACH from portable HEPA units.
Does placement matter?
Yes — spread units around the room rather than clustering them for even mixing.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.