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Commercial Kitchen Ventilation Hood Exhaust CFM Calculator

Calculate the minimum exhaust airflow for an unlisted Type I commercial kitchen hood, per International Mechanical Code duty-rate tables.

Computed in your browser — nothing you enter is uploaded. Figures are presented in United States units and terminology, and each formula’s basis is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax
8 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Minimum required exhaust airflow

2,400 CFM

High confidence

This is the IMC Table 507.5 code-minimum rate for UNLISTED, field-fabricated Type I hoods. A listed hood tested per UL 710 may qualify for a lower manufacturer-published exhaust rate — check the specific hood's listing and manufacturer data before finalizing exhaust fan selection.

Hood length in feet
8 ft
CFM per linear foot rate used
300 CFM/ft

Running these inputs gives 2400 CFM as the minimum required exhaust airflow. Currently reading for United States — pick a different market above and the figures re-cast accordingly.

Add the equipment this sizes

This result is a specification — 2,400 CFM — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.

Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Regulatory standards & verification citations

  • CFM = hood length (linear ft) x CFM-per-linear-foot rate, selected by hood style and cooking-duty classification, per International Mechanical Code (IMC) Table 507.5 (the code-minimum method for unlisted/field-fabricated Type I hoods; NFPA 96 references the same duty classifications). Listed hoods tested per UL 710 may use lower manufacturer-published rates instead — this table is the code-minimum for unlisted hood construction. When a hood covers mixed-duty appliances, code requires using the rate for the heaviest-duty appliance under the entire hood length.

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Frequently asked questions

Why does hood style change the required CFM?
Island hoods are exposed to cross-drafts on all sides and pull air less efficiently than a wall-mounted canopy hood set against a wall, so IMC Table 507.5 assigns island hoods a higher CFM-per-linear-foot rate than a wall-mounted canopy hood of the same duty level.
What happens if a hood covers appliances of different duty levels?
Code requires using the rate for the heaviest-duty appliance located anywhere under the hood across its entire length — you cannot use a lower rate for the portion of the hood over lighter-duty appliances.
Can a listed hood use a lower exhaust rate than this calculator shows?
Yes — this calculator applies the IMC Table 507.5 code-minimum rate for unlisted, field-fabricated Type I hoods. A hood listed and tested per UL 710 may qualify for a lower manufacturer-published exhaust rate, so check the specific hood's listing and manufacturer data before finalizing exhaust fan selection.