Use the calculator below to estimate required exhaust airflow (CFM), compare linear and area-based sizing methods, and generate a practical starting point for fan and makeup air design. Then review the in-depth guide for code context, design strategy, and commissioning best practices.
Enter your hood geometry and cooking duty, then click Calculate.
Commercial kitchen hood exhaust calculation is the engineering process used to determine how much air must be removed from a cooking space to capture grease-laden vapors, heat, smoke, and combustion byproducts at the source. Correct exhaust sizing is a cornerstone of life safety, indoor air quality, fire risk mitigation, and thermal comfort. If airflow is too low, the hood can fail capture and containment, causing smoke spill and odor transfer into dining or adjacent areas. If airflow is excessively high, the project can suffer from unnecessary fan energy, make-up air heating/cooling penalties, noise, and pressure imbalance.
A robust design balances code compliance, kitchen process needs, and practical operation. It starts with hood geometry, appliance duty, and arrangement, then expands to include duct static pressure, filtration type, fan selection, makeup air strategy, and commissioning verification.
This approach multiplies hood length by a duty-and-hood-type factor expressed as CFM per linear foot. It is widely used for conceptual design and quick feasibility checks. It is straightforward and fast, especially during schematic design where detailed equipment schedules are still evolving.
This method calculates airflow from hood plan area and target capture velocity. It can better reflect plume behavior in specific layouts, especially when mounting heights are higher or equipment placement is complex. A style multiplier is commonly used because island hoods generally require more airflow than wall hoods for equivalent duty due to cross-draft exposure and capture geometry.
In many projects, both methods are calculated and the larger value is selected as a conservative preliminary basis until manufacturer submittals and final code review are complete.
Commercial kitchen ventilation does not rely on a single universal number. Requirements vary by local adoption and amendment cycle. Design teams typically coordinate the following references:
Always treat early CFM tools as preliminary engineering aids. Construction documents and permits should reflect jurisdiction-approved values and listed equipment constraints.
Wall canopy hoods generally perform more efficiently at lower airflow than island hoods because the wall acts as a barrier that improves plume containment. Island and double-island hoods are exposed to drafts from multiple directions and typically require higher exhaust rates to maintain capture. Backshelf/proximity hoods can be effective at lower rates when they are correctly matched to appliance type and production process.
Every cubic foot of exhaust removed from the kitchen must be replaced. Without controlled makeup air, the building can become over-negative, leading to hard-opening doors, pilot outage issues, poor thermal comfort, and backdraft risks. Good design usually targets approximately 80–90% of exhaust as dedicated makeup air, with the remainder supplied through transfer or conditioned outdoor air strategy that preserves overall pressure relationships.
Supply discharge velocity and location matter as much as quantity. Air dumped aggressively at hood face can disrupt the thermal plume and degrade capture, even when exhaust CFM appears sufficient on paper.
Sizing airflow alone is not enough. The selected fan must deliver required CFM at actual total static pressure, accounting for duct length, fittings, grease duct velocity requirements, hood collar loss, roof curb loss, and pollution control components if present. Underestimating static pressure is a common cause of field underperformance.
DCKV systems modulate exhaust and makeup air based on real-time cooking load using temperature and/or optical sensing. Properly configured DCKV can reduce fan energy and makeup air conditioning costs while maintaining safety capture performance during high-load periods. Sequence-of-operations quality is critical: minimum turndown limits, coordinated supply tracking, and fail-safe behavior must be clearly defined.
Even a perfectly designed system can degrade quickly without maintenance. Grease accumulation increases pressure drop, lowers effective airflow, and raises fire risk. Establish documented cleaning intervals for hoods, filters, ducts, and fans based on cooking volume and duty type. Replace damaged baffles promptly and keep records aligned with local fire marshal expectations.
A 14-foot wall canopy serving medium-to-heavy production may calculate around 4,200 to 5,600 CFM via linear factors before allowances. If mounting height is above standard and cross-drafts are present, the final design target can increase further. With an 85% makeup air target, dedicated supply could land around 3,600 to 5,000 CFM depending on selected exhaust point and balancing strategy.
Use it for planning and preliminary engineering only. Permit documents should rely on approved code pathways, equipment listings, and stamped design where required.
Moderate contingency is reasonable, but large oversizing can create energy and comfort penalties. Verify capture through testing and commissioning rather than relying on excessive CFM.
Design for the dominant high-intensity segment or consider zoning and hood segmentation where practical. Manufacturer guidance and local code interpretation should govern final values.