Range Hood CFM: How Many CFM Do You Need?
Range hood CFM (cubic feet per minute) measures how much air a hood's blower can move. Get it right and smoke, grease and heat leave the kitchen. Get it wrong and you either fill the house with cooking smells or pay for a loud blower and a makeup air system you didn't need.
Here's the quick answer to "how many CFM do I need?" For a gas range or cooktop, plan on about 1 CFM for every 100 BTU of total burner output. For electric or induction, plan on about 100 CFM per 10 inches of cooktop width against a wall, or about 150 CFM per 10 inches for an island. Make the hood at least as wide as the cooktop, and check local code once you go above 400 CFM, because many US jurisdictions require makeup air at that point.
Use the calculator below for your setup, then read on for hood width, duct size and makeup air basics.
Range hood CFM calculator
Range hood CFM calculator
Rules of thumb only: about 1 CFM per 100 BTU for gas; about 100 CFM per 10″ of width for electric/induction (150 for islands). Many areas require makeup air above 400 CFM: check local code and the hood maker’s specs.
The calculator applies the rules of thumb in this guide. Treat the result as a starting point for a conversation with your designer, HVAC contractor or dealer, not a final spec.
How many CFM do you need for a gas range?
Gas burners make heat, moisture and combustion byproducts in addition to cooking fumes, so they need the most airflow. The common rule of thumb is 1 CFM per 100 BTU of total burner output. Add up every burner (and a gas griddle, if you have one), then divide by 100.
Here's how that works with real ranges on this site:
| Range | Total cooktop output | Suggested CFM |
|---|---|---|
| Thermador Pro Harmony 36-inch gas | 120,000 BTU | about 1,200 |
| Fisher & Paykel Series 9 36-inch dual fuel | 121,000 BTU | about 1,210 |
| Wolf 36-inch gas range (GR366) | about 84,200 BTU (5 x 15,000 + 9,200, per one retailer) | about 840 |
Two 36-inch ranges can land hundreds of CFM apart, which is why the burner math matters more than the width. If your range spec sheet doesn't list total output, add up the individual burner ratings. For big 48-inch ranges with a griddle or charbroiler, totals climb fast. See our best 48-inch ranges and best 36-inch ranges for options.
Remember that the 1-per-100 rule assumes all burners at full blast. Many cooks don't need the full number every day. That's why multi-speed blowers and heat sensors are useful: the hood can run quietly most of the time and ramp up for a hard sear.
How many CFM do you need for induction or electric?
Induction and electric cooktops don't burn fuel, so you're only removing cooking fumes, steam and grease. Size by width instead of BTU:
- Against a wall: about 100 CFM per 10 inches of cooktop width. A 36-inch induction cooktop works out to about 360 CFM.
- On an island: about 150 CFM per 10 inches, since there's no wall to help contain the plume. A 36-inch island cooktop works out to about 540 CFM.
That's a big reason induction can simplify ventilation. A 36-inch induction cooktop against a wall may stay under the 400 CFM makeup air threshold, while most 36-inch gas ranges won't. If you're still deciding on fuel, read our gas vs induction guide and browse the best induction ranges and cooktops.
How wide should a range hood be?
CFM is only half the job. A hood has to capture the smoke before it can exhaust it, and capture depends on size and position.
- Wall hoods: at least as wide as the cooktop. Many designers go wider on a pro-style gas range for better capture.
- Island hoods: go 3 to 6 inches wider than the cooktop, because cross-drafts push smoke sideways.
- Depth: deeper hoods capture more of the front burners. The Wolf 36-inch pro wall hood is offered in 24-inch and 27-inch depths.
- Mounting height: follow the manufacturer's range. Wolf lists 30 to 36 inches above the cooking surface for its pro wall hood. Higher looks more open but captures less.
A properly sized hood mounted too high, or too narrow for the cooktop, will still let smoke escape.
Makeup air: what happens above 400 CFM
When a hood pushes air out, the same amount of air has to come back in. In a tight modern house, a powerful hood can struggle to pull air, get louder, and in the worst case draw exhaust from other gas appliances back into the home.
That's why many US jurisdictions follow the International Residential Code requirement (IRC M1503.6) that calls for makeup air when a kitchen exhaust hood can move more than 400 CFM. Makeup air systems bring outdoor air back into the house, often through a motorized damper tied to the hood, and sometimes with heating to temper cold air.
Rules and enforcement vary by city and county, so check local code with your contractor or building department before you order. Makeup air can add meaningful cost and needs to be planned with your HVAC system, not added at the end.
Duct size basics
Your duct can make or break a hood's real-world performance. Rated CFM is measured under ideal conditions. Long runs, many elbows and undersized ducts all reduce it.
- Use the duct size the hood maker specifies, and never reduce it. The Zephyr Monsoon Connect insert (700 CFM) specifies 8-inch round duct, and the Wolf pro wall hood uses 10-inch round. Higher CFM generally means a bigger duct.
- Keep the run short and straight. Each elbow and each extra foot adds resistance.
- Use smooth, rigid metal duct. Flexible duct creates more resistance and traps grease.
- Vent outdoors. Terminate at a proper wall or roof cap with a damper, never into an attic, soffit or wall cavity.
- Plan the route early. Joists, beams and upstairs rooms can block the path, so map it before you pick a hood.
Noise: sones and blower placement
More CFM usually means more noise. Hoods list noise in sones. The Vent-A-Hood Premier 36-inch (600 CFM) lists 6.5 sones at maximum, while the Zephyr insert lists 0.8 to 6 sones across its speeds.
Blower placement also matters. Wolf's pro wall hood is sold as a shell, with internal blowers from 300 to 1,200 CFM or inline and remote blowers from 600 to 1,500 CFM, chosen separately. Owners and installers commonly report that moving the blower away from the hood, inline in the duct or on the roof, makes a hood quieter in the kitchen. Note that Wolf's list price of about $2,585 is the hood shell only; the blower is extra.
Common range hood CFM mistakes
- Buying the biggest blower available. Oversizing can trigger makeup air requirements, add cost and create drafts without improving capture.
- Ignoring capture area. A narrow or shallow hood loses smoke no matter how strong the blower.
- Recirculating over gas. Recirculating kits exist, including for Wolf's pro hood, but they filter rather than remove heat, moisture and combustion byproducts. Ducting outdoors is the better choice for gas.
- Forgetting the duct. A great hood on a long, kinked or undersized run underperforms.
Compare complete hood options in our best range hoods list and on the ventilation hub.
Frequently asked questions
How many CFM do I need for a 36-inch gas range?
Use about 1 CFM per 100 BTU of total burner output. The Thermador Pro Harmony 36-inch gas range has 120,000 BTU total, so about 1,200 CFM. A Wolf GR366, at about 84,200 BTU by one retailer's figures, works out to about 840 CFM. Both are above 400 CFM, so check your local makeup air requirements.
How many CFM do I need for an induction cooktop?
Against a wall, plan on about 100 CFM per 10 inches of cooktop width, so roughly 360 CFM for a 36-inch induction cooktop. On an island, plan on about 150 CFM per 10 inches, or roughly 540 CFM. Induction produces no combustion byproducts, so it typically needs less airflow than gas, but it still needs real ventilation.
Do I need makeup air for my range hood?
Many US jurisdictions follow IRC M1503.6, which requires makeup air when a kitchen exhaust hood can move more than 400 CFM. Most hoods for 36-inch and larger gas ranges exceed that. Rules and enforcement vary locally, so check with your contractor or building department before you buy, and plan makeup air alongside your HVAC system.
Is more CFM always better?
No. Capture area, hood width, mounting height and duct design matter as much as blower power. An oversized blower can add noise, create drafts, trigger makeup air requirements and raise costs without removing more smoke. Size the hood to your cooktop's output, make it at least as wide as the cooktop, and use the duct size the manufacturer specifies.
What size duct do I need for a range hood?
Use the size the hood manufacturer specifies and never reduce it along the run. On this site, the 700 CFM Zephyr Monsoon Connect insert calls for 8-inch round duct and the Wolf pro wall hood uses 10-inch round. Higher-CFM hoods generally need larger ducts. Keep runs short, use smooth rigid metal and vent outdoors.