How to Size an Upblast Exhaust Fan: A CFM Guide for Commercial Kitchens
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How to Size an Upblast Exhaust Fan
Choosing the right upblast exhaust fan comes down to one number: CFM (cubic feet per minute), the volume of air your fan pulls through the hood. Undersize it and grease, smoke, and heat linger in your kitchen — and you fail inspection. Oversize it and you waste money conditioning air you blow straight outside. Here is how to size an upblast exhaust fan for a commercial kitchen the practical way.
1. Start with your hood
Exhaust CFM is driven by your Type 1 (grease) hood — its length, style (wall-mounted vs island), and the equipment underneath it. As a rule of thumb, a wall-mounted canopy hood needs roughly 200–300 CFM per linear foot, and a heavy-duty line (a charbroiler pulls far more than a steam table) pushes that higher. Your hood manufacturer or local code official will give you the exact required exhaust CFM — that figure is what your fan must match.
2. Match the fan to the required CFM
Pick an upblast fan rated at or just above your hood's required exhaust CFM at the static pressure of your duct run. Direct-drive centrifugal upblast fans (no belts to slip or replace) are the standard for commercial kitchens because they handle grease-laden air and high static pressure reliably. Common sizes:
- 2050 CFM (1/2 HP) — small kitchens, a single short hood, food trucks
- 2500 CFM (3/4 HP) — a typical restaurant cook line
- 4000 CFM (1 HP) — large hoods, heavy frying, high-volume kitchens
3. Do not forget make-up air
Every cubic foot you exhaust has to be replaced. Code requires make-up air (typically around 80% of exhaust volume) so your kitchen stays pressure-balanced — otherwise doors slam, pilot lights blow out, and your fan starves. Size a make-up air unit to roughly match your exhaust CFM.
4. Confirm code compliance
Commercial kitchen exhaust is governed by NFPA 96 and the International Mechanical Code (IMC). Your fan must be grease-rated, and your full system — hood, duct, fan, make-up air, and fire suppression — has to meet those standards to pass inspection. When in doubt, check with your local authority having jurisdiction.
Still not sure?
Send us your hood dimensions and cooking equipment and we will help you size the right fan for free. Browse every model on our upblast exhaust fans page — grease-rated, NFPA 96-ready, and priced at wholesale.