How to size a range hood for a Florida kitchen.

How Much CFM You Need

For most Florida kitchens, a range hood lands between 300 and 600 CFM: enough to clear smoke, grease, and steam from the cooktop without crossing the line where the code demands engineered makeup air. CFM — CFM, cubic feet of air moved per minute — is the headline spec, but it is the wrong place to start shopping. Width and cooktop type set the target first; CFM follows.

Two simple rules carry most of the decision. Gas burners are sized by heat: roughly 1 CFM per 100 BTU of total burner output. Electric and induction surfaces are sized by size: about 100 CFM per linear foot of cooktop. Everything after that — duct length, mounting height, whether the kitchen is open to the living room — adjusts the number up or down.

Get the Width and Overhang Right First

A hood that is too narrow lets smoke and grease spill past its edges no matter how much air it moves. The capture area has to physically sit over the cooking surface, so width is the first spec to lock — before CFM, before brand, before finish.

Match the cooktop, then add overhang

The baseline rule is that the hood spans the full width of the cooktop. Capture improves when the hood is wider still, with about 3 in of overhang on each side — roughly 6 in of extra width overall. A 30 in cooktop pairs naturally with a 36 in hood; a 36 in cooktop with a 42 in hood. The overhang catches the plume that rises and spreads as it leaves the back burners.

Why overhang matters more in Florida

Florida kitchens run their air conditioning hard, and the supply registers create cross-drafts that push a cooking plume sideways before the hood can grab it. A hood sized exactly to the cooktop, with no margin, loses that contest. The overhang is cheap insurance against re-circulated grease film settling on cabinets and the cooler interior surfaces where humidity already encourages residue.

Mounting height interacts with width

A taller mounting clearance spreads the plume wider by the time it reaches the hood, so a hood hung high needs the full overhang to keep working. Follow the manufacturer's specified clearance above the cooktop; do not split the difference to clear a window or a cabinet without rechecking capture.

• 30 in cooktop pairs with a 36 in hood for full 3 in overhang on each side.
• 36 in cooktop pairs with a 42 in hood; pro-style ranges scale the same way.
• Island installs want extra width because the plume is exposed to drafts on all sides.

Lock the width before anything else, because no amount of CFM rescues a hood that physically does not sit over the food.

Sizing for a Gas vs Electric Cooktop

The fuel decides the math. Gas releases combustion byproducts and far more raw heat than a coil or induction surface, so a gas cooktop needs more airflow per inch of width than an electric one of the same size. Size to the heat for gas, and to the width for electric.

Gas: 1 CFM per 100 BTU

Add up the rated BTU of every burner — the figure is on the spec label or in the manual — and divide by 100. A cooktop totaling 40,000 BTU points to about 400 CFM; a 60,000-BTU pro-style unit points toward 600. The Home Ventilating Institute frames the 1-CFM-per-100-BTU ratio as a reasonable starting point, then duct length and mounting height fine-tune it.

Electric and induction: 100 CFM per linear foot

Resistance and induction cooktops generate steam and a little smoke but no combustion gases, so the demand is lower. Allow roughly 100 CFM for every 10 in of cooktop width — a 30 in cooktop wants about 300 CFM as a floor. Heavy searing or wok cooking justifies stepping up from there.

Gas cooktop

Sized to heat. Total BTU ÷ 100 = target CFM. Combustion byproducts make adequate, ducted ventilation a safety item, not just a comfort one.

Electric / induction cooktop

Sized to width. About 100 CFM per linear foot; less smoke means a lower floor, and a ductless unit is more defensible here than over gas.

Whichever fuel you cook on, treat these formulas as a starting target and let the realities below — the 400-CFM line and the duct run — pull the final number into range.

The 400-CFM Makeup-Air Line

This is the Florida-specific ceiling that catches homeowners off guard. Under IRC Section M1503.4 — adopted through the Florida Building Code — any kitchen exhaust system capable of moving more than 400 CFM must be paired with a makeup-air system that supplies replacement air at approximately the same rate, interlocked to run with the hood.

Why a tight house cannot feed a big blower

A modern, well-sealed, air-conditioned Florida home leaks very little air. Run a 600- or 900-CFM blower in that envelope and it pulls a partial vacuum, because the air it ejects has nowhere to come back in. The result is backdrafting risk at any combustion appliance and a hood that underperforms its own rating.

What backdrafting actually means

If the house has a gas water heater, furnace, or fireplace that vents naturally, negative pressure can reverse that flue and draw combustion gases — including carbon monoxide — back into the living space. That is the safety logic behind the 400-CFM trigger, not a paperwork formality.

The practical takeaway is to size honestly: a hood that genuinely needs 600 CFM should get the makeup air the code requires rather than a quieter, undersized blower that never clears the plume.

Ducted vs Ductless: Which Is Better

For a Florida kitchen, a ducted hood that carries air outdoors is the better choice; a recirculating (ductless) hood filters and returns air to the room. The difference is decisive in this climate because a recirculating unit removes neither heat nor moisture — it hands both back to an air-conditioned space already fighting humidity.

What recirculating filters can and cannot do

A ductless hood pulls cooking air through a charcoal filter that traps some odor and grease, then blows it back into the kitchen. It cannot exhaust steam, and it cannot exhaust heat. In Florida that means the latent moisture from boiling and the warmth from the burners stay in the room, loading the air conditioner and feeding the conditions mold prefers.

When ductless is defensible

Over an electric or induction cooktop used for light cooking, where running a duct to the exterior is genuinely impossible, a high-quality recirculating unit is a fallback. It is rarely the right answer over gas, which produces both more heat and combustion byproducts that belong outdoors.

In a humid, cooled home the moisture and heat columns are what settle the argument: a ducted hood ejects both, while a ductless one returns them to the room you are paying to keep cool and dry.

Venting It Out an Exterior Wall

The shortest, straightest path to the outdoors is the best duct, and on most Florida slab-on-grade homes that path runs horizontally out the nearest exterior wall rather than up through the roof. Short and straight preserves the hood's rated airflow; bends and length steal it.

Duct material and termination the code requires

Per IRC Section M1503.3, a single-wall range-hood duct must be galvanized steel, stainless steel, or copper, with a smooth interior, an airtight seam, and a backdraft damper. It must discharge to the outdoors and may not terminate in an attic, a crawl space, or any concealed area inside the building.

Wall-cap and damper detail

The exterior termination needs a wall cap with its own backdraft damper so humid outside air and salt-laden coastal moisture cannot drift back into the duct between cooking sessions. On a coastal home, a corrosion-resistant cap earns its keep.

• Backdraft damper at the cap blocks humid Gulf and Atlantic air from migrating inward when the hood is off.
• Corrosion-resistant finish resists salt-air pitting on coastal terminations.
• Sealed penetration keeps wind-driven rain out of the wall assembly.

Those three details are what keep a wall-vented hood from becoming a moisture entry point in a climate that punishes any gap.

Done in that order, a short horizontal run lets a 300-to-400-CFM hood perform at its rating and keeps the install on the easy side of the makeup-air line. A kitchen remodel is the moment to route this correctly, which is why our full kitchen remodeling scope coordinates the duct, the electrical, and the wall penetration together.

Sizing It Step by Step

Putting the pieces in order keeps a Florida hood both effective and code-clean. Width sets the floor, fuel sets the airflow, and the 400-CFM line sets the ceiling before you ever look at a brand.

That sequence usually lands a Florida kitchen at a ducted hood in the 300-to-600-CFM band, sized to the cooktop and vented out the nearest wall. Where a remodel touches walls, lighting, or layout at the same time, our kitchen lighting plan and general contracting teams sequence the hood with the rest of the work, and the wider Florida kitchen remodeling guide frames how ventilation fits the whole project.