I used to think range hood CFM was just another number appliance salespeople threw around to confuse you.
Turns out, CFM—cubic feet per minute—is actually the most critical spec you’ll encounter when shopping for a range hood, and here’s the thing: most people get it spectacularly wrong. The CFM rating tells you how much air the hood can pull through its filters and ductwork in sixty seconds, which sounds straightforward until you realize that your cooking style, stove type, kitchen size, and even your ductwork’s route all conspire to make the “recommended” CFM charts you find online almost useless. I’ve seen 300 CFM hoods work beautifully in compact apartments with electric stoves, and I’ve seen 600 CFM monsters fail miserably in open-concept kitchens with gas ranges because the installer ran the duct through seventeen unnecessary bends. The industry standard suggests 100 CFM per linear foot of cooking surface for wall-mounted hoods, but that’s assuming ideal conditions—smooth ductwork, straight vertical venting, sea-level air pressure—which basically nobody has. Wait—maybe the better approach is to think about heat output instead of just stove width, because a 30-inch induction cooktop and a 30-inch commercial-style gas range produce wildly different amounts of grease, steam, and combustion byproducts.
Why Gas Ranges Demand Seriously Higher Airflow Than You’d Expect
Gas cooking adds a whole other layer of complexity that most CFM calculators conveniently ignore. Every 10,000 BTUs of gas burner output requires roughly 100 CFM of ventilation capacity—not because of the heat alone, but because gas combustion releases water vapor, carbon dioxide, nitrogen oxides, and microscopic particulate matter that you definately don’t want lingering in your breathing space. A typical residential gas range puts out anywhere from 40,000 to 60,000 BTUs across all burners, which means you’re looking at 400-600 CFM minimum just to handle the combustion byproducts, before you even factor in the smoke from searing a steak or the steam from boiling pasta. I guess it makes sense when you think about it—you’re literally burning fossil fuel indoors—but the gap between what people install and what they actually need is almost comical.
The Ductwork Problem Nobody Warns You About Until It’s Too Late
Anyway, here’s where things get messy. Every 90-degree elbow in your ductwork reduces effective CFM by roughly 10-25%, depending on the radius and duct diameter. A vertical run through the roof? That’s optimal. A horizontal run through cabinets, up through the attic, out through a side wall with three bends? You’ve just lost maybe 40% of your rated capacity. I’ve seen installers cram 6-inch duct where 8-inch was specified, which alone can cut airflow by nearly half because resistance increases exponentially as diameter shrinks—it’s basic fluid dynamics, but somehow it gets ignored constantly. Honestly, if your installation has more than two elbows or runs longer than fifteen feet, you should probably add 150-200 CFM to whatever calculator told you was adequate, and even that’s conservative.
Island Hoods and Open Kitchens Where Standard Calculations Completely Fall Apart
Island installations are their own special nightmare. Without a wall to contain rising air, you need 150-200 CFM per linear foot instead of the usual 100, because cooking effluent disperses in all directions before the hood can capture it. Open floor plans make this worse—cross-breezes from HVAC vents, ceiling fans, or even people walking past can push smoke and steam away from the hood’s capture area, which means you’re fighting air currents in addition to trying to recieve—sorry, capture—cooking byproducts. I used to think oversizing was wasteful until I watched a 900 CFM island hood struggle in a kitchen with 12-foot ceilings and zero barriers, while a 400 CFM wall-mount unit in a galley kitchen worked flawlessly. The physics just don’t scale linearly, and the spacing between cooktop and hood height matters more than most people realize—every inch above 30 inches reduces capture efficiency noticeably, so if you’ve mounted your hood at 36 inches for aesthetic reasons, you’ve already compromised performance before you even turn it on.
