Workshop Exhaust Fan Calculator
General exhaust airflow for a home workshop.
Enter your values
ⓘ Live results
Results
- Required exhaust
- 768 CFM
- Shop volume
- 5,760 cu ft
- Fan at 6 in duct, 1200 FPM
- 3911 FPM check
- Intake louvre area at 500 FPM
- 1.54 sq ft
Quick answer
Workshops are generally ventilated at 6-10 air changes per hour for general fume and dust dilution, more for solvent-heavy or welding work.
CFM = volume x ACH / 60
How to use the Workshop Exhaust Fan Calculator
- 1Calculate the workshop volume from its dimensions.
- 2Choose an air-change rate based on the work being done — higher for painting or welding.
- 3Size a matching fresh air intake so the fan is not starved.
Worked example
Using the values the calculator loads with:
Inputs
- Shop length24 ft
- Shop width24 ft
- Ceiling height10 ft
- Air changes8 ACH
Results
- Required exhaust768 CFM
- Shop volume5,760 cu ft
- Fan at 6 in duct, 1200 FPM3911 FPM check
- Intake louvre area at 500 FPM1.54 sq ft
Frequently asked questions
Do I need spot extraction too?
Yes for welding, sanding or solvent use — general exhaust dilutes background fumes but does not replace source capture.
Can a box fan in a window work?
For light hobby use yes, but it will not meet the ACH target of a properly ducted exhaust fan.
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.