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Estimate net exhaust CFM from hood length, canopy style, and the highest appliance duty under the hood. This commercial kitchen ventilation calculator uses IMC 2021 prescriptive rates for unlisted wall-mounted or single-island canopy hoods. It is early planning, not a permit design or a substitute for a listed hood's approved installation data.
Estimated net hood exhaust
3,000CFM
Planning estimate using IMC 2021 §507.5 unlisted canopy rates, not a permit design. Listed hoods, local amendments, makeup air, fire suppression, duct losses, and capture testing require professional review. Dengaro is a financing broker and a brand of Funding Routes LLC, not the lender. No approval or rate is promised.
How it works
This hood cfm calculator multiplies the hood's front-face length in feet by the applicable CFM per linear foot. For wall-mounted canopies, light, medium, heavy, and extra-heavy duty use 200, 300, 400, and 550 CFM per foot. Single-island canopies use 400, 500, 600, and 700 CFM per foot. These are the unlisted-canopy rates in IMC 2021 sections 507.5.1 through 507.5.4; adopted editions and local amendments may differ. Use the highest appliance duty for the whole hood, rather than averaging the appliances. Net exhaust excludes air supplied directly into the hood cavity. This commercial kitchen hood calculator does not size a fan motor, grease duct, makeup air unit, or fire-suppression system. A mechanical designer must coordinate the whole system and the local authority's requirements.
Formula
Wall canopy rates: light 200, medium 300, heavy 400, extra-heavy 550 CFM/ft. Single-island rates: 400, 500, 600, and 700 CFM/ft respectively. Measure the front-face length, not perimeter or square footage. The equivalent flow in liters per second is CFM × 0.47194745.
Example
Ten feet × 300 CFM/ft = 3,000 CFM of net exhaust, about 1,415.84 L/s. The same length and duty with a single-island canopy uses 500 CFM/ft, giving 5,000 CFM. A heavy-duty wall canopy at 10 feet instead gives 4,000 CFM. These differences reflect the selected hood style and highest appliance duty, not a fan-efficiency adjustment.
Tips
Listed hood exhaust can differ from these unlisted-hood rates. Confirm duty classifications for the exact appliances and fuel, including solid-fuel equipment. Makeup air, transfer air, capture and containment, cross drafts, overhang, mounting height, grease filters, duct static pressure, and fire suppression all affect the design. Air changes per hour for the room cannot replace cooking-hood capture requirements.
Equipment
Get a supplier quote for the hood, exhaust fan, and any eligible ventilation equipment after professional sizing. Any budget price is an estimate, not a financing offer. Dengaro is a financing broker and a brand of Funding Routes LLC, not the lender. The CTA is for kitchen equipment financing; no airflow or job-cost result is passed as a loan amount, and approval or rates are not promised.
Important questions
No. It is a planning calculation using specified unlisted-canopy rates. The adopted code, local amendments, appliance lineup, hood listing, makeup air, and capture testing must be reviewed by a qualified designer and the local authority before installation.
Use the highest applicable appliance duty for the entire hood. Do not average light and heavy equipment. Appliance duty depends on equipment type and fuel, not just temperature or how often it is used; confirm classifications under the adopted code.
Not directly. Listed hoods follow their approved performance and installation data. Type II dishwashing hoods, proximity hoods, double-island hoods, and residential range hoods have other requirements and are outside the two canopy styles supported here.
No universal percentage is calculated here. A designer must balance dedicated makeup air, HVAC outdoor air, transfer air, other exhaust, and building pressure. Air supplied directly into the hood cavity does not count toward the net exhaust result shown.
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