Welding Fume Extraction CFM Calculator
Capture airflow for a welding hood or arm.
Enter your values
ⓘ Live results
Results
- Extraction airflow
- 840 CFM
- Unflanged requirement
- 1,120 CFM
- Saving from flange
- 280 CFM
- At half the distance
- 278 CFM
Working
- 1100 x (10 x 1² + 1.2) = 1,120 CFM
Quick answer
Capture airflow rises with the square of distance, so getting the hood close is far more effective than buying a bigger fan.
CFM = V x (10 x X² + A) for a plain hood
How to use the Welding Fume Extraction CFM Calculator
- 1Measure how far the hood face sits from the arc or fume source.
- 2Enter the hood face area and required capture velocity — 100 FPM suits welding.
- 3Add a flange to the hood; it cuts required airflow by about 25%.
Worked example
Using the values the calculator loads with:
Inputs
- Capture distance1 ft
- Hood face area1.2 sq ft
- Capture velocity100 FPM
- Flanged hood?Yes
Results
- Extraction airflow840 CFM
- Unflanged requirement1,120 CFM
- Saving from flange280 CFM
- At half the distance278 CFM
- 100 x (10 x 1² + 1.2) = 1,120 CFM
Frequently asked questions
Why does distance matter so much?
Required airflow grows with the square of distance, so doubling the gap roughly quadruples the fan you need.
Is general ventilation enough?
No — local exhaust at source is the only reliable control for welding fume.
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.