Vacuum CFM Calculator
Airflow and pipe size for a vacuum system.
Enter your values
ⓘ Live results
Results
- Airflow
- 136 CFM
- Hose area
- 0.0341 sq ft
- Velocity
- 4,000 FPM
- Chip conveying minimum
- 3500-4000 FPM
- In m³/h
- 232
Quick answer
Vacuum airflow equals hose cross-sectional area multiplied by air velocity, the same relationship as any duct.
CFM = area (sq ft) x FPM
How to use the Vacuum CFM Calculator
- 1Measure the hose or pipe inside diameter.
- 2Use 3,500-4,000 FPM to keep chips and dust airborne.
- 3Match the vacuum's rated CFM at your actual static pressure, not free air.
Worked example
Using the values the calculator loads with:
Inputs
- Hose diameter2.5 in
- Air velocity4000 FPM
Results
- Airflow136 CFM
- Hose area0.0341 sq ft
- Velocity4,000 FPM
- Chip conveying minimum3500-4000 FPM
- In m³/h232
Frequently asked questions
Why does hose length matter?
Long small-bore hose adds huge resistance — a 2.5 in hose at 30 ft can halve the airflow.
Shop vac vs dust collector?
Shop vacs are high suction, low flow; dust collectors are the opposite and suit large machines.
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.