Workshop Exhaust Fan Calculator
General exhaust airflow for a home workshop.
Enter your values
Enter the shop length in ft.
Enter the shop width in ft.
Enter the ceiling height in ft.
Enter the air changes in ACH.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | General exhaust airflow for a home workshop. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Shop length, Shop width, Ceiling height, Air changes |
| Main output | Required exhaust |
| Formula | CFM = volume x ACH / 60 |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Shop length(ft)
- Enter the shop length in ft.
- Shop width(ft)
- Enter the shop width in ft.
- Ceiling height(ft)
- Enter the ceiling height in ft.
- Air changes(ACH)
- Enter the air changes in ACH.
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.
What do I need to enter into the Workshop Exhaust Fan Calculator?
Just 4 values: shop length, shop width, ceiling height, air changes. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Workshop Exhaust Fan Calculator work out the 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. It applies the formula CFM = volume x ACH / 60 and shows the working so you can check each step by hand.
Is the Workshop Exhaust Fan Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.