🍲 HVAC

Free Online Kitchen Exhaust Hood Airflow Calculator

Calculate commercial kitchen hood exhaust CFM and make-up air from hood length, cooking duty and canopy style. IMC / NFPA 96 basis. Free online tool, no sign-up.

📐 Standard: NFPA 96
✅ Free to use
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Kitchen Exhaust Hood Airflow Calculator
Reference: NFPA 96
🍲 HVAC
Calculate commercial kitchen hood exhaust CFM and make-up air from hood length, cooking duty and canopy style. IMC / NFPA 96 basis. Free online tool, no sign-up.
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ℹ️ About This Calculator

A commercial kitchen hood must capture and remove cooking heat, smoke and grease-laden vapour. This calculator estimates the exhaust airflow in CFM and m³/h, the required make-up air and a grease-duct size from the hood length, cooking duty and canopy style, following IMC / NFPA 96 practice.

Exhaust volume is driven by the cooking equipment's duty - light (ovens, steamers), medium (ranges, fryers) or heavy (charbroilers, woks) - expressed as CFM per linear foot of hood. Make-up air replaces roughly 80-90% of the exhaust to avoid depressurising the kitchen, and the grease duct is sized for at least the NFPA 96 minimum velocity of 500 fpm.

📐 Kitchen Hood Exhaust Formula (NFPA 96 / IMC)

NFPA 96

Q = L(ft) × rate × style
Make-up air = Q × 0.85
Grease duct area = Q / 1500

Q = exhaust airflow, CFM
L = hood length, ft
rate = 200-400 CFM/ft by cooking duty
style = 1.0 wall-mounted, 1.4 island canopy
duct velocity = 1500 fpm (NFPA 96 min 500)

🧮 Worked Example

Example: A 2 m (6.56 ft) wall-mounted canopy over medium-duty cooking equipment at 300 CFM/ft gives Q = 6.56 × 300 × 1.0 ≈ 1969 CFM (3345 m³/h). Make-up air at 85% is about 1673 CFM, and the grease duct at 1500 fpm needs roughly 349 mm square.

❓ Frequently Asked Questions

How many CFM does a commercial kitchen hood need? +
It depends on hood length and cooking duty. Wall-mounted canopies run about 200 CFM per linear foot for light duty, 300 for medium and 400 for heavy duty. Island hoods need roughly 40% more because they entrain air from all sides.
How much make-up air does a kitchen exhaust need? +
Make-up air should replace about 80-90% of the exhaust volume. Providing too little depressurises the kitchen, causes door-pull problems and back-drafts appliances; the balance (10-20%) is typically drawn from the adjacent dining space.
What is the difference between a wall and island kitchen hood? +
A wall-mounted canopy has a wall on one side that helps contain the plume, so it needs less airflow. An island (single or double) hood is open on all sides and must exhaust roughly 1.4 times more air to capture the same cooking effluent.
What velocity should a grease exhaust duct run at? +
NFPA 96 requires a minimum of 500 fpm to keep grease entrained and prevent settling, with 1000-1500 fpm common in practice. This calculator sizes the duct at 1500 fpm; higher velocities reduce grease build-up but raise fan pressure.
Does hood duty type change the exhaust rate? +
Yes. Heavy-duty equipment such as charbroilers and woks produces far more heat and smoke than light-duty ovens, so the CFM-per-foot rate roughly doubles from light to heavy duty for the same hood length.

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⚠️ Disclaimer: For preliminary engineering design only. Verify all results with a licensed engineer before use. Full disclaimer →