Range Hood Buying Guide: CFM Sizing, Ducted vs Ductless Recirculating, and Noise Ratings (2026)

A range hood is a kitchen ventilation appliance that captures the buoyant plume of grease, steam, and combustion byproducts rising from a cooktop and either exhausts it outdoors through a duct or filters it and returns it to the room. It is the only appliance in the kitchen whose primary function is defensive — it removes contaminants rather than cooking food — and its performance cannot be perceived the way a refrigerator's temperature or a dishwasher's cleanliness can. Four independent engineering parameters determine whether a hood performs that defensive function or merely makes noise above the stove: the airflow capacity measured in cubic feet per minute (CFM) and whether it is correctly matched to the cooktop's output, the exhaust path that separates ducted ventilation from ductless recirculation, the noise rating in sones and the placement of the blower that determines whether the hood is tolerable at the airflow required to do the job, and the capture geometry that decides whether the plume is actually intercepted in the first place.

CFM Sizing: Matching Airflow to the Cooktop

The airflow capacity of a range hood is rated in cubic feet per minute (CFM), the volume of air the blower moves at a given static pressure. The specification is meaningful only in relation to the cooktop it serves, because the hood's job is to out-pace the rate at which cooking effluent is produced. The governing sizing rules derive from the cooktop's fuel type and heat output. For an electric cooktop, the standard guidance is 100 CFM per linear foot of cooktop width, which produces a minimum of roughly 250 to 300 CFM for a typical 30-inch range. For a gas cooktop, the guidance is 100 CFM per 10,000 BTU/hr of total burner output; a four-burner gas range rated at 40,000 to 50,000 BTU/hr therefore calls for 400 to 500 CFM, and a pro-style six-burner range approaching 80,000 BTU/hr warrants 600 to 900 CFM.

The distinction between the two rules reflects what each fuel emits. An electric cooktop produces heat, steam, and grease aerosols; a gas cooktop produces all of those plus the combustion byproducts of the flame itself — carbon dioxide, water vapor, nitrogen oxides, and carbon monoxide at low concentrations. The gas rule accounts for that additional load, which is why the minimum meaningful specification for a hood over gas is generally stated as 400 CFM regardless of the arithmetic. A hood rated below its cooktop's demand leaves smoke and odor stratifying at the ceiling, deposits a grease film on cabinets and walls, and, over gas, allows combustion byproducts to accumulate in the living space. A hood rated far above the demand wastes energy, raises the noise floor, and — above the 400 CFM threshold discussed under building code — triggers a make-up air requirement that can add thousands of dollars to the installation.

Two caveats govern how the rated CFM should be read. First, the rating is an airflow figure measured by the Home Ventilating Institute (HVI) at a standardized static pressure of 0.1 inch of water gauge; it is not the airflow the hood delivers once installed. Every foot of duct, every elbow, and every transition imposes flow resistance that reduces the delivered CFM, so a hood rated 600 CFM at the blower may move 400 CFM through a restrictive 6-inch duct run with two bends. Second, CFM is not interchangeable with capture efficiency: a hood can move a large volume of air and still fail to capture the plume if its geometry is wrong, a point addressed in the capture section below. Airflow is a necessary condition for effective ventilation, not a sufficient one.

Ducted vs Ductless Recirculating

The exhaust path is the single most consequential decision in range hood selection, because it determines what the hood is physically capable of removing. A ducted hood connects the blower to a rigid duct that terminates outdoors through a wall or roof, and it removes everything the cooktop emits: grease, steam, heat, odor, and combustion gases. A ductless (recirculating) hood contains no duct connection; the blower draws the plume through a grease filter and a replaceable activated-carbon filter and returns the cleaned air to the kitchen. The recirculating configuration removes airborne grease and a meaningful fraction of odor, but it cannot remove moisture, heat, or combustion byproducts, because those are gases that a carbon filter does not capture and that no filter can condense. A recirculating hood over a gas cooktop therefore leaves the water vapor and nitrogen oxides from combustion in the room, a consideration that argues strongly for ducted ventilation wherever gas is involved.

The choice between the two configurations is usually dictated by the building, not by preference. A kitchen on an interior wall, or an apartment where no wall or roof penetration is permitted, may offer no practical duct path, and a recirculating hood is then the only option. In that situation the carbon filter becomes a maintenance item with a defined service life — it must be replaced every three to six months depending on cooking frequency, at a cost of roughly $15 to $40 per filter — and a hood whose filter is exhausted recirculates air that is barely cleaner than the plume it draws. The carbon filter also imposes a static-pressure penalty that reduces delivered airflow, so the effective ventilation of a recirculating hood declines progressively between filter changes. When a duct path does exist, ducted ventilation is superior on every functional axis, and the incremental cost of the ductwork — typically $200 to $600 for a short run with one penetration — is the single best investment in kitchen air quality available at the appliance level.

The recirculating configuration is not valueless. Over an electric cooktop in a well-ventilated home, it removes the grease aerosol that is the dominant nuisance, and it does so without the thermal penalty of exhausting conditioned air to the outdoors — a ducted hood pulling 400 CFM continuously removes heated or cooled indoor air that must be replaced, which is precisely the energy-loss mechanism that building codes now address with make-up air. But the honest framing is that recirculation is a compromise imposed by the building, not an equal alternative, and it should be understood as such before the purchase is made.

Duct Design and Static Pressure

The ductwork between the hood and the outdoors is part of the ventilation system, and its design determines how much of the blower's rated CFM actually reaches the termination. The governing variable is static pressure, the resistance the blower must overcome, and it accumulates with every component in the run. The dominant factors are duct diameter, the number and radius of the elbows, the total length, and the material of the duct itself.

Duct diameter is matched to airflow, and the failure to match it is the most common installation defect. The practical ranges are: a 6-inch round duct supports airflow up to roughly 400 CFM; a 7-inch duct supports 400 to 600 CFM; an 8-inch duct supports 600 to 900 CFM; and 10-inch duct is required above that. A hood with a 600 CFM blower connected to a 6-inch duct will not deliver 600 CFM — the duct throttles the blower, raising the static pressure, reducing the airflow, and increasing the noise, because the blower is working harder against the restriction. The corollary is that the duct must never be reduced below the diameter of the blower's discharge collar; a 7-inch collar mated to a 6-inch duct through a reducer discards airflow at the point of greatest resistance.

Elbows and length are the second and third factors. Each 90-degree elbow adds a pressure drop equivalent to roughly 10 to 15 feet of straight duct, so a run with three elbows performs like a straight run three times its nominal length. Smooth, long-radius elbows impose less resistance than tight, short-radius fittings. Flexible accordion duct — the foil or vinyl tubing sometimes substituted for rigid duct — has a corrugated interior that imposes dramatically higher resistance than smooth galvanized steel, and it is a poor choice for any range hood operating above 300 CFM. Rigid galvanized duct, assembled with the joints sealed with foil tape and the seam oriented to drain condensate, is the standard against which everything else is measured. The termination matters as well: a wall cap or roof cap with a backdraft damper prevents outdoor air and pests from entering when the blower is off, and a cap with a restricted free area adds its own pressure drop that a hood's installed airflow reflects.

The practical consequence of all of this is that airflow is a system property, not a blower property. Two hoods with identical blowers will deliver different CFM through different duct runs, and a hood advertised at 600 CFM may be out-performed in the field by a hood advertised at 400 CFM connected to a short, straight, properly sized duct. When comparing hoods, the duct plan should be designed before the blower is chosen, because the blower must be sized to overcome the duct that the building actually permits.

Noise Ratings: Sones and Blower Placement

Range hood noise is rated in sones, a unit of perceived loudness rather than of sound pressure. The sone scale is linear in the way human hearing is not: one sone is approximately the loudness of a quiet refrigerator from a few feet away, four sones is roughly the level of normal conversation, and eight sones is the level at which a hood becomes unpleasant to stand near. Because the scale is perceptual, doubling the sone value corresponds to a doubling of perceived loudness, which is why the difference between a 1.5-sone hood and a 6-sone hood is not a factor of four on paper but a genuinely different experience in the kitchen. HVI certifies sone ratings at a standardized airflow, so the rating is comparable across manufacturers, but the airflow at which it is measured must be noted: a hood advertised as "quiet" at its lowest speed may be rated at 6 sones at the maximum speed where it actually does its work.

The relationship between airflow and noise is fundamental and inescapable: moving more air makes more noise. A hood that genuinely delivers 600 CFM cannot be as quiet as one delivering 300 CFM, all else equal, because the noise is generated by the blower moving air and by the air moving through the duct. The engineering variable that breaks this trade-off is blower placement, which exists in three configurations. An internal blower mounts inside the hood canopy, directly above the cooktop where the operator's head is, and it is the loudest option because the noise source is closest to the listener. An inline blower mounts in the duct run, typically in the attic or between floor joists, moving the noise source away from the kitchen and producing a substantially quieter hood for the same airflow. A remote (exterior) blower mounts on the roof or an exterior wall, outside the living envelope entirely, and it is the quietest configuration — the hood canopy contains only the duct and controls — at the cost of the highest installation complexity. For a hood that will be run at 600 CFM or more with any regularity, an inline or remote blower is the difference between a ventilation system that is used and one that is avoided because it is too loud to run.

For daily operation, the rating that matters most is the sone value at the low and medium speeds, because those are the speeds a hood runs at during ordinary cooking. A hood rated 0.3 to 1.5 sones on low is effectively inaudible over the sound of cooking itself; a hood rated 3 sones or more on low will be heard continuously. The maximum-speed rating matters for the occasional high-output sear, and it is where the blower-placement decision is felt most acutely. Buyers should compare sone ratings at a matched CFM, not at the hood's own arbitrary speed steps, because two hoods with the same maximum-speed sone rating may move very different volumes of air at that setting.

Capture Geometry: Width, Depth, and Mounting Height

Airflow and capture are distinct properties, and a hood can fail at its job while moving a large volume of air if its geometry does not actually intercept the plume. The plume is not a tidy column: it expands as it rises, and it is pushed sideways by the cross-drafts of people walking past, by the convection of the cooktop itself, and by the turbulence of frying. The hood's physical envelope must be large enough and low enough to contain the plume at the height where it is captured.

The governing dimensions are width, depth, and mounting height. The hood should be at least as wide as the cooktop, and ideally three inches wider on each side, so that the expanding plume is still within the capture envelope at the hood's intake plane; a 30-inch hood over a 30-inch range captures the center of the plume while allowing the edges to spill past. Depth is the dimension most often undersized. A cooktop is 24 to 25 inches deep, and an under-cabinet hood of 18 to 20 inches deep leaves the front burners — where the most aggressive cooking happens — outside the capture envelope. Pro-style and island hoods are 24 to 27 inches deep precisely so that the front burners fall under the intake. The rule is simple: the hood must project far enough forward that the front burners are beneath it.

Mounting height is the third dimension, and it trades capture against clearance and fire safety. The standard range is 24 to 30 inches above an electric cooktop and 27 to 30 inches above a gas cooktop, with some manufacturers permitting up to 36 inches for pro-style hoods at the cost of reduced capture. Mounting a hood higher than the recommended range degrades capture rapidly, because the plume expands and slows before reaching the intake and cross-drafts win; mounting it lower improves capture but creates a head-clearance hazard and, over a flame, a grease-fire risk. The mounting-height specification is a genuine safety constraint, not a suggestion, and it is one of the few hood specifications that should not be bent to fit cabinetry.

Capture efficiency — the fraction of the cooking effluent actually drawn into the hood — is the composite output of these three dimensions, and it is the reason a deep, low, wide hood at 400 CFM can outperform a shallow, high, narrow hood at 700 CFM. The airflow rating gets the attention in marketing, but capture geometry is what determines whether the airflow is applied to the plume or to the surrounding room air.

Grease Filtration and Blower Type

The grease filter is the first stage of every range hood, and its design determines both the maintenance burden and the long-term airflow. Two filter types dominate. Baffle filters are formed stainless-steel channels arranged in an overlapping pattern that forces the air to change direction sharply, slinging the grease droplets onto the metal by inertia while the air passes through. They are dishwasher-safe, do not need replacement, and — because the air path through them is comparatively open — they maintain their airflow as they load with grease. Mesh filters are layered aluminum screens that intercept grease by straining; they capture fine aerosols effectively when clean, but their small openings clog quickly, and a loaded mesh filter restricts airflow and forces the blower to work harder. Both types require periodic cleaning, but the baffle filter is the design that dominates pro-style and high-CFM hoods, and it is the correct default for any hood that will see real cooking.

Charcoal filters are a third category, but they serve only the recirculating configuration described earlier, where they substitute for a duct by adsorbing odor compounds. They do not filter grease and do not remove moisture, and their finite adsorption capacity is why recirculating hoods require a recurring filter purchase that ducted hoods do not.

The blower itself is a centrifugal squirrel-cage fan in well-engineered hoods, preferred over an axial propeller because the centrifugal design develops the static pressure required to push air through a duct run. Blower quality is rarely specified in a way the buyer can evaluate, but its consequences appear in two observable places: the sone rating, and the hood's behavior as the grease filter loads. A blower with adequate pressure reserve maintains airflow as the filter and duct accumulate resistance; a marginal blower loses airflow quickly under the same conditions. Multi-speed control is standard, and the features that genuinely affect use are a delayed shutoff that continues ventilation for several minutes after cooking ends to clear residual plume, and a heat sensor that raises the speed automatically when the cooktop temperature climbs.

Make-Up Air and Building Code

The building-code constraint that most directly shapes range hood selection is the make-up air requirement in the International Residential Code. Under section M1503.4, a range hood that exhausts more than 400 CFM must be provided with a mechanical make-up air system that supplies replacement air from outdoors at approximately the rate of the exhaust. The requirement exists because a powerful exhaust blower depressurizes the house: it removes air faster than the building's natural infiltration replaces it, which can backdraft naturally aspirated gas appliances — the water heater, the furnace, the fireplace — and pull carbon monoxide into the living space. Make-up air systems, which typically include a motorized damper, a pressure switch, and frequently a heater to temper the incoming air, cost on the order of $1,000 to $3,000 installed.

The practical implication is that the 400 CFM threshold functions as a de facto ceiling for most residential installations. A homeowner who selects a 600 CFM hood over a gas range may discover that the purchase triggers a make-up air system that costs more than the hood itself, and a contractor who installs the hood without it has produced an installation that is non-compliant and, in a tightly built home, potentially unsafe. The threshold is not universal — local amendments and the tightening of the code over successive editions vary the number and, in some jurisdictions, apply a lower threshold to small or unusually tight homes — but 400 CFM is the planning figure that should be assumed unless the local authority confirms otherwise. For households that do not require more than 400 CFM of airflow, staying under the threshold is the single most effective way to contain installation cost, and it is why a correctly sized hood for a standard 30-inch range frequently lands at or just under the threshold rather than well above it.

Comparing the Options: A Decision Matrix

The choice of range hood reduces to four decisions — airflow and its match to the cooktop, the exhaust path, the blower placement and noise budget, and the capture geometry — each of which determines a distinct aspect of the ventilation system and cannot be fully compensated for by the others.

Notable manufacturers across the category include Broan-NuTone, the dominant volume brand whose under-cabinet and wall-mount hoods span the $60 to $500 range and cover the budget and mid tiers comprehensively; Cosmo, which concentrates on low-cost wall-mount and island hoods in the $150 to $400 range; Hauslane, a direct-to-consumer brand whose stainless baffle-filter hoods at $300 to $700 have made it a fixture in kitchen renovations; Zephyr, which spans $300 to $1,500 and offers inline and remote blower options that the value brands do not; and Vent-A-Hood, a Texas manufacturer whose proprietary "Magic Lung" centrifugal design at $1,000 to $3,000 anchors the premium tier alongside ZLINE, a popular mid-priced brand of pro-style stainless hoods.

A well-engineered range hood for a standard 30-inch cooktop is a ducted wall-mount or under-cabinet unit with a centrifugal blower rated between 300 and 400 CFM — enough for a gas range's combustion load while remaining under the make-up air threshold — fitted with stainless baffle filters, a canopy at least 24 inches deep to cover the front burners, and a low-speed sone rating at or below 1.5 so that it is actually used. That specification, available from Broan-NuTone, Cosmo, or Hauslane in the $150 to $500 range, represents the threshold at which kitchen ventilation transitions from a nominal fixture to a system that removes grease, moisture, and odor from the air the household actually breathes. Households with a high-output or pro-style range, or a cooktop on an island requiring a deep canopy and long duct run, are better served by a 600-plus CFM hood with an inline or remote blower from Zephyr or Vent-A-Hood — and should budget for the make-up air system that the code, correctly, will require.