HEPA Room ACH Calculator
Number of HEPA units for a target ACH.
Enter your values
Enter the room area in sq ft.
Enter the ceiling height in ft.
Enter the target air changes in ACH.
Enter the cfm per hepa unit in CFM.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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)
At a glance
| What it does | Number of HEPA units for a target ACH. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Room area, Ceiling height, Target air changes, CFM per HEPA unit |
| Main output | Total airflow needed |
| Formula | Units = (ACH x volume) / (60 x unit CFM) |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Room area(sq ft)
- Enter the room area in sq ft.
- Ceiling height(ft)
- Enter the ceiling height in ft.
- Target air changes(ACH)
- Enter the target air changes in ACH.
- CFM per HEPA unit(CFM)
- Enter the cfm per hepa unit in CFM.
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.
What do I need to enter into the HEPA Room ACH Calculator?
Just 4 values: room area, ceiling height, target air changes, cfm per hepa unit. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the HEPA Room ACH Calculator work out the 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. It applies the formula Units = (ACH x volume) / (60 x unit CFM) and shows the working so you can check each step by hand.
Is the HEPA Room ACH Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.