HEPA Filter Airflow Calculator
Face velocity and airflow for a HEPA filter.
Enter your values
ⓘ Live results
Results
- Airflow
- 1,000 CFM
- Face area
- 4 sq ft
- Estimated pressure drop
- 1 in wc
- Change-out drop (2x)
- 2 in wc
- In m³/h
- 1,699
Quick answer
HEPA filters are rated near 250-500 FPM face velocity; going higher pushes pressure drop up steeply.
CFM = face area (sq ft) x face velocity
How to use the HEPA Filter Airflow Calculator
- 1Enter the filter panel dimensions and target face velocity.
- 2Check the pressure drop against the fan's available static.
- 3Replace at roughly double the clean pressure drop.
Worked example
Using the values the calculator loads with:
Inputs
- Filter width24 in
- Filter height24 in
- Face velocity250 FPM
- Rated clean drop1.0 in wc
Results
- Airflow1,000 CFM
- Face area4 sq ft
- Estimated pressure drop1 in wc
- Change-out drop (2x)2 in wc
- In m³/h1,699
Frequently asked questions
Can HEPA go in a home furnace?
Only with a purpose-built bypass cabinet and booster fan — a standard blower cannot overcome the drop.
True HEPA?
99.97% capture at 0.3 microns; anything labelled HEPA-type is not certified.
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.