Range Hood CFM Explained (2026): How Much Suction You Actually Need by Cooktop

Range hood CFM (cubic feet per minute) is the most marketed and least understood specification in kitchen ventilation. Hood manufacturers compete on max CFM numbers like horsepower wars in the 1990s muscle car era. Most of those numbers describe lab-condition airflow with no ducting losses, in a hood that will never perform at that number in a real kitchen. This guide breaks down what CFM actually means, how to size a hood for real cooking, and how installation conditions wreck the marketed performance.

What CFM actually measures

CFM in range hood spec sheets is the volumetric airflow rate the hood can move under ideal lab conditions: short straight ducting, no elbows, no transition losses, the hood new and clean. The number is honest as a hood capability rating but misleading as an installation prediction.

In a real installation, the actual airflow at the cooktop is determined by:

The hood’s max capability (the marketed CFM).

The ducting system: diameter, length, number of elbows, transitions, and roof or wall termination cap restriction.

The grease filter condition: clean filters pass airflow freely, oil-saturated filters reduce airflow 20 to 40 percent.

The hood height above the cooktop: higher hoods capture less of the rising plume even at the same CFM.

Make-up air availability: tight houses without make-up air systems starve the hood, dropping actual CFM 30 to 60 percent.

A 1,200 CFM hood with a 25-foot run of 6-inch flexible ducting, four elbows, and a saturated grease filter in a tight house with no make-up air can deliver less than 300 CFM actual airflow at the cooktop. That is not a defect of the hood; it is the result of the installation conditions.

Sizing by cooktop type

The HVI (Home Ventilation Institute) guideline for residential cooktops:

Electric cooktop: 100 CFM per linear foot of cooktop width. A 30-inch electric cooktop needs about 250 CFM actual.

Gas cooktop, standard residential: 100 CFM per 10,000 BTU of total cooktop output. A typical 30-inch gas cooktop with 60,000 BTU total needs about 600 CFM actual.

Gas cooktop, professional-style (commercial-style sealed burners, 18,000-plus BTU max): 150 to 200 CFM per 10,000 BTU. A 36-inch pro-style range with 75,000 BTU total needs about 1,100 to 1,500 CFM actual.

Induction cooktop: 80 CFM per linear foot. Induction produces less thermal plume because it heats the pan directly rather than radiating heat into the room. A 36-inch induction cooktop needs about 250 to 300 CFM actual.

Wok cooking, indoor grills, or specialty high-heat use: add 30 to 50 percent to the base requirement.

These are actual CFM at the cooktop, not marketed CFM on the hood spec sheet. Account for the ducting losses by selecting a hood with marketed CFM about 50 to 100 percent above the actual target. A 600 CFM target wants a 900 to 1,200 CFM marketed hood with proper ducting.

Ducting matters more than CFM

The single biggest determinant of real-world hood performance is ducting. The CFM marketing focuses on the hood; the ducting silently destroys most of it.

Duct diameter matters most. The static pressure loss in a duct scales with the square of velocity, which scales inversely with the square of diameter. Doubling the duct diameter cuts the static pressure loss by a factor of 16 at the same airflow. A 6-inch duct that works fine for a 400 CFM hood becomes a major restriction at 1,200 CFM. A 1,200 CFM hood needs at least 8-inch round (or equivalent rectangular) ducting; 10-inch is better.

Duct length matters. Each foot of straight ducting adds a small static pressure loss. A 5-foot run is negligible; a 25-foot run takes a 15 to 25 percent bite out of actual airflow.

Elbows matter most of all on a per-element basis. A 90-degree elbow adds the equivalent of about 8 to 12 feet of straight duct in static pressure loss. Two 90-degree elbows in series wreck airflow more than 20 feet of straight duct. Sweep elbows (long-radius) are dramatically better than tight elbows.

Flex duct is much worse than rigid duct at the same diameter because the corrugated interior creates turbulence and increases friction loss. Rigid galvanized steel or rigid aluminum is the right choice for hood ducting. Use flex duct only for the final 1 to 2 feet to the hood connection.

The roof or wall termination cap matters. A high-quality termination cap with a smooth flapper damper adds minimal restriction. A cheap mesh-covered cap can restrict airflow 20-plus percent.

Make-up air rules

In modern tight-construction homes (post-2010 with air sealing per energy codes), the house leakage rate is low enough that a high-CFM hood can create significant negative pressure inside the house. The hood is trying to push 800-plus CFM of air outside; the air has to come from somewhere.

Without a dedicated make-up air system, the air infiltrates around door seals, through HVAC return ducts, down chimneys, and through any other unsealed pathway. The infiltration creates a few problems:

Backdrafting of combustion appliances: a gas furnace, water heater, or fireplace with a natural-draft chimney can reverse flow under enough negative pressure, pulling combustion gases (including carbon monoxide) into the house instead of up the chimney. This is the most dangerous failure mode.

Cold or hot air infiltration: in winter, cold outside air gets pulled in around windows and doors, dropping interior temperature. In summer, hot humid air gets pulled in.

Reduced hood performance: the hood is fighting the static pressure rise, which drops the actual CFM at the cooktop.

The 2024 IRC and many state codes require a make-up air system for hoods rated above 400 CFM in many jurisdictions. The make-up air system is a powered duct from outside that opens automatically when the hood is on, providing matched airflow to replace what the hood exhausts. Cost: $400 to $1,500 added to the install.

Marketing CFM vs real CFM

To translate the marketed CFM number to what you actually get at the cooktop, a rough rule:

For a hood with rigid ducting, 8-inch or larger, two or fewer elbows, run under 15 feet, clean filters, and make-up air provided: actual CFM is about 80 to 90 percent of marketed.

For a hood with 6-inch ducting or one with three-plus elbows or run over 20 feet or no make-up air on a tight house: actual CFM is 40 to 60 percent of marketed.

For a hood with flex ducting throughout or installed in a worst-case combination of restrictions: actual CFM can drop to 20 to 30 percent of marketed.

This is why a kitchen with a 600 CFM hood that has good ducting often performs better than a kitchen with a 1,200 CFM hood that has bad ducting. The number on the box is not the number at the cooktop.

Sizing recommendations by kitchen

For an electric or induction cooktop in a standard kitchen: 300 to 500 CFM marketed hood with reasonable ducting. Plenty of suction for the lower thermal plume.

For a standard 30-inch gas range in a standard kitchen: 600 to 900 CFM marketed hood with proper 7 or 8-inch ducting and make-up air on tight homes.

For a 36-inch high-BTU gas range or pro-style range: 900 to 1,500 CFM marketed hood, 8-inch ducting minimum, sweep elbows, short run, make-up air required.

For a 48-inch professional range or indoor grill: 1,500 to 2,500 CFM marketed hood, 10-inch ducting, make-up air mandatory by code in most jurisdictions.

The hood is part of the kitchen ventilation system, not just an appliance to buy on CFM specs. Get the ducting right and any reasonable hood will perform well. Get the ducting wrong and no hood will save the install. For more on kitchen ventilation, see our methodology page.

Frequently asked questions