How is commercial kitchen hood exhaust airflow sized?

Exhaust airflow is the hood length times the capture depth times the duty-based face velocity; NFPA 96 sets the minimum face velocity by cooking duty.

How much make-up air does a kitchen hood need?

Make-up air is typically sized at about 80% of the exhaust airflow so the kitchen stays slightly negative without starving the hood.

What duct velocity is required for a grease duct?

NFPA 96 requires a minimum grease-duct velocity of 500 feet per minute to keep grease entrained and prevent build-up on the duct walls.

How is commercial kitchen hood exhaust airflow sized?

Exhaust airflow is the hood length times the capture depth times the duty-based face velocity. NFPA 96 sets the minimum face velocity by cooking duty, from light duty through extra-heavy charbroiling.

How much make-up air does a kitchen hood need?

Make-up air is typically sized at about 80% of the exhaust airflow so the kitchen stays slightly negative without starving the hood or pulling air from the dining room.

What duct velocity is required for a grease duct?

NFPA 96 requires a minimum grease-duct velocity of 500 feet per minute to keep grease entrained and prevent build-up on the duct walls.

Command Center

Instrument online

Commercial Kitchen Hood Sizer

Size exhaust hoods and make-up air for commercial cooking lines per NFPA 96.

Hood Geometry & Duty

Mounting

Wall-mounted canopy over a single cooking line, open on three sides.

IMC 507 / NFPA 96 duty class

Ranges, ovens, and medium-duty griddles.

Cooking lineup length

Hood depth (W)

Side / front overhang

Winter ΔT

°F

Overhang compliant — 6 in ≥ 6 in minimum

Grease Duct & Filters

Target duct velocity

fpm

UL 1046 baffle filter

Computed Readouts

Compliant

Hood length: 108.0
Exhaust airflow: 2,700
Make-up air: 2,295
Duct area: 1.800
Round duct: 18.2
Rectangular duct: 22.8 × 11.4
Baffle filters: 7
MUA heater load: 99,144

Overhang6 / 6 in min

Duct velocity1,500 fpm · in target

Live Hood Blueprint

Hardware BOM

7 lines · 13 units

Item	Specification	Qty
Wall Canopy exhaust hoodHD-WALL-CANOPY	Type I · Medium · 108 in × 30 in	1 ea
UL 1046 baffle filters — 16 × 20 inUL 1046	Type I grease filters · stainless steel	7 ea
Grease ductNFPA 96	Round 18.2 in dia · 1500 fpm target	1 run
Grease duct collar	18.2 in dia · welded liquid-tight	1 ea
Upblast exhaust fan	2,700 cfm · grease-rated	1 ea
Make-up air unit	2,295 cfm · 99,144 BTU/hr heater	1 ea
Make-up air diffuser	Perforated supply plenum · 2,295 cfm	1 ea

Worked Formula

Step 1L_hood = L_lineup + 2 × OverhangL_hood = 96.0 + 2 × 6.0L_hood = 108.0 in (9.00 ft)
Step 2CFM_exhaust = L_hood × CFM_per_ft × IslandFactorCFM_exhaust = 9.00 × 300 × 1.00CFM_exhaust = 2,700 cfm
Step 3CFM_MUA = CFM_exhaust × 0.85CFM_MUA = 2,700 × 0.85CFM_MUA = 2,295 cfm
Step 4A_duct = CFM_exhaust / VA_duct = 2,700 / 1,500A_duct = 1.800 ft²
Step 5D_round = 12 × √(4 × A_duct / π)D_round = 12 × √(4 × 1.800 / π)D_round = 18.2 in
Step 6BTU/hr = 1.08 × CFM_MUA × ΔTBTU/hr = 1.08 × 2,295 × 40BTU/hr = 99,144

Governing Formulas

Q = L × D × VExhaust airflow (cfm)
Q_makeup = Q × 0.8Make-up air (cfm)
V_duct = Q / A_ductDuct velocity (fpm)
H_hood = L + 2 × overhangHood length (ft)

Frequently Asked Questions

How is commercial kitchen hood exhaust airflow sized?: Exhaust airflow is the hood length times the capture depth times the duty-based face velocity. NFPA 96 sets the minimum face velocity by cooking duty, from light duty through extra-heavy charbroiling.
How much make-up air does a kitchen hood need?: Make-up air is typically sized at about 80% of the exhaust airflow so the kitchen stays slightly negative without starving the hood or pulling air from the dining room.
What duct velocity is required for a grease duct?: NFPA 96 requires a minimum grease-duct velocity of 500 feet per minute to keep grease entrained and prevent build-up on the duct walls.

Related Calculators

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Commercial Kitchen Hood Sizer Presets

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