Range hood CFM calculator: how big a hood your kitchen needs

How many CFM does a range hood need?

The Home Ventilating Institute Publication 916 sets the residential standard most manufacturers follow, and it gives you three sizing methods that should all be run. The correct hood is whichever method returns the highest CFM, since the kitchen has to handle the worst case. The methods are: 100 CFM per linear foot of stove width for wall and under-cabinet hoods (150 CFM per foot for island hoods), 1 CFM per 100 BTU/hr of total gas burner output, and the kitchen volume divided by 4 minutes (which is 15 air changes per hour). A 30 inch wall hood over a 45,000 BTU/hr gas range in a 200 square foot kitchen with 9 foot ceilings would run 250, 450, and 450 CFM respectively. The hood gets sized to the 450 number.

The calculator above runs all three methods at once so you can see why one number wins. Take the recommended CFM and round up to the nearest catalog size, which is usually 400, 600, 900, or 1200 CFM. Hoods are not sold in arbitrary increments and rated CFM should be treated as a minimum, not a target, because real installed airflow always comes in below the spec sheet.

How to size a range hood for a gas stove

Gas cooktops are the loudest case for high CFM because the burner releases combustion products you actually need to capture (water vapor, carbon monoxide, NO2, ultrafine particles). The 1 CFM per 100 BTU/hr rule scales the hood to the burner. Add the BTU rating of every burner on the cooktop spec sheet to get the total. Typical numbers:

• Builder-grade 4-burner gas range: 30,000 to 40,000 BTU/hr total, needs 300 to 400 CFM
• Standard 30 inch gas range with one power burner: 40,000 to 55,000 BTU/hr, needs 400 to 550 CFM
• 36 inch gas range with five or six burners: 55,000 to 75,000 BTU/hr, needs 600 to 750 CFM
• 48 inch pro-style range (Wolf, Viking, Thermador): 75,000 to 120,000 BTU/hr, needs 800 to 1,200 CFM
• 60 inch dual-fuel pro range with griddle: 100,000 to 150,000 BTU/hr, needs 1,000 to 1,500 CFM

Whatever number the BTU method gives you, do not go below 250 CFM in any kitchen with a gas stove. Lawrence Berkeley National Laboratory studies on indoor air quality consistently find homes with gas cooking and undersized hoods exceeding EPA NO2 limits within minutes of starting a burner. The CFM is not about smoke. It is about pulling combustion byproducts out of the room before they reach the breathing zone.

Electric and induction range hoods: lower CFM but still needed

Electric and induction cooktops produce no combustion byproducts, so the BTU method does not apply. Sizing comes from the stove width method alone, with a 150 CFM floor for any real installation. A 30 inch induction cooktop in an open kitchen needs 250 to 400 CFM, which captures grease aerosols, steam, and odor. Skipping the hood entirely (which some homeowners do with induction because it feels cleaner) leaves grease film on cabinets, moisture on windows, and cooking odors that linger for hours.

The other reason to install a real hood over induction is grease capture. Sautéing, searing, and stir-frying release oil aerosols that the cooktop technology does not change. A 350 CFM hood with a good baffle filter pulls the grease into the filter where it belongs, instead of letting it settle on the upper cabinets and become a cleaning project every six months.

How kitchen size changes range hood CFM

The room volume method is the third sizing check. Multiply kitchen floor area by ceiling height to get cubic feet, then divide by 4 (which is the 15 air changes per hour HVI target expressed as a divisor). A 250 square foot kitchen with 9 foot ceilings is 2,250 cubic feet, divided by 4 is 565 CFM. That number tells you how much air the hood needs to move to actually clear the cooking plume from the whole room within four minutes of cooking ending.

Open-concept kitchens that flow into a living room or great room throw off the volume method because the air mass is much bigger than the kitchen footprint suggests. The practical fix is to size by stove width and BTU only in those layouts, and ignore the volume number. Closed galley kitchens at the other extreme can over-recommend volume CFM because the small enclosed space concentrates the cooking plume more than a typical room. Sanity-check the final number against the stove width result before buying a 1,200 CFM hood for a 90 square foot galley.

Ductwork derate: why your hood underperforms the spec sheet

Rated CFM on the box is measured at zero static pressure with the fan running into open air. Real installed performance is always lower because the duct adds resistance. Add 1 CFM of derating per linear foot of straight smooth metal duct, 25 CFM per 90 degree elbow, and 40 CFM for the wall or roof cap. A typical 15 foot duct run with two elbows and a roof cap costs you 105 CFM (15 + 50 + 40), which means a 400 CFM hood is actually delivering about 295 CFM at the cooktop.

Flex duct multiplies the straight-run loss by about 1.5 because the rough inner wall creates more friction. Cheap aluminum flex on a 20 foot run with three elbows easily costs 150 to 200 CFM, which puts a 600 CFM hood at real-world 400 CFM and a 400 CFM hood at 200 CFM. Smooth galvanized steel duct is the right call on every install over 8 feet. It runs $4 to $8 per linear foot, the joints seal with foil tape and screws, and a contractor can fabricate a clean run in 2 to 3 hours. The cost difference between flex and smooth metal on a typical install is $80 to $150, which is almost always worth it for the airflow you keep.

Makeup air: when IRC code requires a fresh air system

IRC M1503.4 and IECC 402.5 require a makeup air system whenever a range hood rated 400 CFM or higher gets installed in a home that meets the energy code's tight-construction threshold (3 air changes per hour at 50 pascals or less, which is most homes built after 2009). Without makeup air, a high-CFM hood depressurizes the house, which can backdraft natural-draft water heaters and furnaces, pull combustion gases down the flue, and pull radon up through the basement slab. The risk is real and the code is enforced.

A makeup air system is a motorized damper plus 6 to 8 inch ducting that opens automatically when the hood runs. Installed cost ranges $400 to $2,000 depending on whether the air is tempered (heated in winter, cooled in summer) or untempered. Untempered systems are cheaper but dump cold or hot outdoor air into the kitchen, which most homeowners find miserable. Tempered systems route the makeup air through the HVAC system or a small inline heater, which costs more but actually works year round. Budget the makeup air system into the hood project from the start, because adding it later after an inspector flags it costs 50 percent more in retrofit labor.

How high should a range hood be installed above the cooktop?

The right install height depends on the heat source. Gas cooktops need 30 to 36 inches of clearance from the burner grate to the bottom of the hood, which is the manufacturer requirement on every residential gas range to prevent heat damage to the hood electronics and grease filter. Electric and induction cooktops can sit closer at 24 to 30 inches because there is no open flame and the plume rises more directly. Going higher than the recommended range hurts capture efficiency by an estimated 5 to 10 percent per 6 inches of extra distance, which is the whole reason the hood exists.

The other clearance to verify is between the hood face and the cook standing at the cooktop. Industry guidance puts the bottom edge of the hood high enough that a 6 foot tall adult does not bump it leaning into the stove. For tall homeowners, the practical compromise is the 36 inch height with a hood that extends 3 to 6 inches forward of the cooktop face, which captures the plume without the head-clearance problem. Verify the install height with the manufacturer instructions before cutting the duct hole.

Duct diameter for range hoods: 6 inch versus 8 inch versus 10 inch

Duct diameter scales with the hood's rated CFM. Going too small chokes the fan and adds significant static pressure, which kills delivered airflow even more than length and elbows do. The HVI minimums:

• Up to 600 CFM: 6 to 8 inch round duct (8 inch is the contractor default)
• 600 to 900 CFM: 7 to 10 inch round duct (8 inch is fine for short runs, 10 inch for runs over 20 feet)
• 900 to 1,200 CFM: 8 to 12 inch round duct (10 inch is the contractor default at this tier)
• 1,200 CFM and above: 10 inch or larger round, never less

Rectangular duct works too, with cross-section equivalents listed in ACCA Manual D. A 10 inch round equals roughly 12 by 6 inch rectangular for the same airflow capacity. Skip the "I will use a 6 inch duct on my 1,200 CFM hood because that is what is already in the wall" instinct. The hood will roar, the bearings will wear, and you will lose half the rated CFM to the undersized duct.

Best range hood brands by CFM tier and use case

For builder-grade kitchens under 400 CFM, Broan-NuTone and Hauslane dominate the box-store channel with reliable hoods in the $200 to $600 range. For mid-tier kitchens needing 500 to 700 CFM, Zephyr, Best by Broan, and Vent-A-Hood are the value picks at $700 to $1,500. Pro-style kitchens needing 900 to 1,500 CFM almost always end up with Vent-A-Hood, Wolf, Miele, or Faber at $2,000 to $5,000 installed. The cheap end is fine for low-CFM electric installs. The pro-style end is where the noise engineering, baffle filter quality, and motor longevity actually justify the price premium.

Whatever brand you pick, verify three things on the spec sheet: rated CFM at the working static pressure of your duct run (HVI-certified hoods publish a fan curve), sone level at standard CFM (under 4 sones is acceptable, under 2 is quiet), and baffle filter type (stainless steel baffles outperform mesh filters at grease capture and last 10+ years). Verify the warranty covers the motor for at least 5 years on the higher-CFM models, where motor failure is the most common reason for replacement.