Dust Collection CFM Calculator
Dust collection CFM starts with port area and target transport velocity, then adds active branches and airflow allowance. Use the working dust collector CFM calculator before comparing fan curves and static pressure.
Airflow formula
For a round tool port, airflow equals port area times target transport velocity.
Q = area * velocity
Branches and allowance
The working calculator multiplies by active same-size branches, then applies an airflow allowance for filter loading, leakage and separators.
Static-pressure boundary
CFM is only the airflow screen. Final collector selection needs duct length, fittings, filters, separator loss and a manufacturer fan curve.
Frequently asked questions
How much CFM does a 4 inch dust port need?
At 4000 ft/min transport velocity, a 4 inch round port screens at about 349 CFM before allowance.
Does this choose a dust collector?
No. It estimates airflow and duct velocity; final equipment selection needs static pressure and fan-curve data.
Related pages
- Dust collector CFM calculator - working port, velocity and branch airflow calculator.
- Dust collector sizing calculator - equipment-selection search path for the same airflow screen.
- Duct size calculator - general round and rectangular duct velocity checks.
- Static pressure calculator - budget pressure losses after airflow is known.
- Woodworking calculators - complete woodshop workflow path.