Formula & worked example
V=Q/A; Arequired=Q/Vtarget.
A 20×25 in filter at 1,000 CFM has about 288 fpm face velocity.
HVAC engineering calculator · Updated Sep 17, 2026
Filter Face Velocity Calculator — CFM, Area & Required Filter Size
Calculate HVAC filter face velocity from airflow and filter dimensions, or reverse-size required gross filter area from a target velocity.
Inputs
Live result
Gross face area 3.4722222 ft²
Face velocity 288 fpm
Required area at target 2.8571429 ft²
Equivalent square 20.283702 in × in
Assumptions & limits
- Uses gross filter face area, not pleated media area.
- Confirm pressure drop and rated airflow with manufacturer data.
Frequently asked questions
What does this Filter Face Velocity Calculator calculate?
Calculate HVAC filter face velocity from airflow and filter dimensions, or reverse-size required gross filter area from a target velocity.
Is this suitable for final equipment selection?
Use it as an auditable engineering cross-check. Final selections should use measured design conditions, manufacturer data, applicable standards and local code.
Why does MAXScanner expose the assumptions?
HVAC shortcuts can hide density, pressure, concentration and effectiveness assumptions. Exposing them makes the result easier to verify and revise.