The CFM you need depends on your stove size and cooking style

CFM stands for cubic feet per minute — it measures how much air your range hood pulls out of the kitchen. A hood that's too weak won't clear smoke and steam. One that's too strong wastes energy and can create drafts that mess with your furnace or water heater. The right size sits between those two problems.

For most home kitchens, you need 100 CFM for every 12 inches of cooktop width. A 30-inch stove needs roughly 250 CFM. A 36-inch stove needs roughly 300 CFM. A 48-inch commercial-style stove needs 600 CFM or more. These are starting points, not rules — your actual need depends on how often you cook, whether you cook with high heat, and how well your kitchen is sealed.

If you cook rarely or mostly use low heat, you can go lower. If you cook daily with a gas stove or wok, you should go higher. Island hoods (which pull from both sides) need about 25 percent more CFM than wall-mounted hoods pulling from one side.

Key Takeaways

  • A basic rule is 100 CFM per 12 inches of cooktop width, so a 36-inch stove typically needs around 300 CFM.
  • Gas stoves and high-heat cooking need more CFM than electric stoves and low-heat cooking.
  • Island hoods need roughly 25 percent more CFM than wall hoods because they pull air from both sides.
  • A hood that's too weak leaves grease and odor in your kitchen; one that's too strong can interfere with your furnace or water heater draft.

How cooktop type and fuel affect CFM needs

Gas stoves produce more heat and moisture than electric stoves, so they need more CFM. A 30-inch gas cooktop typically needs 250 to 300 CFM, while a 30-inch electric cooktop may only need 150 to 200 CFM. If you have a gas range with a powerful burner or you use a wok, add another 50 to 100 CFM.

Induction cooktops produce less steam than gas or electric coil, so they can work with slightly lower CFM. However, induction stoves do generate some heat, so don't go below the baseline calculation for your cooktop width.

Downdraft cooktops (which pull air down through the cooking surface instead of up through a wall hood) typically need 300 to 600 CFM because they fight gravity and have to pull air across a wider area. Wall-mounted and under-cabinet hoods are more efficient at the same CFM.

Ducting and installation affect real-world performance

The CFM rating on a hood's box is measured in ideal conditions — short, straight ductwork with no bends. Real kitchens have longer runs, elbows, and dampers. Every 10 feet of ductwork and every 90-degree elbow reduces the hood's actual CFM by roughly 10 to 15 percent. A hood rated 300 CFM with 20 feet of ductwork and two elbows may only deliver 240 CFM in your kitchen.

If your ductwork is long or has many turns, buy a hood rated 25 to 50 percent higher than your baseline calculation. A 300 CFM hood becomes a 375 to 450 CFM hood. Smooth, rigid metal ductwork loses less air than flexible ducting, so if you have a choice, rigid is better.

Ductwork diameter also matters. A 6-inch duct is standard for residential hoods up to 400 CFM. Larger hoods need 7-inch or 8-inch ducts. Undersized ducts choke the hood and waste its power.

Wall-mounted versus island hoods

A wall-mounted hood (also called a range hood or under-cabinet hood) sits directly above or behind your stove and pulls air in one direction. It's the most efficient design because air has a short, direct path to the duct.

An island hood hangs from the ceiling above a cooktop in the middle of the room. It has to pull air from all sides, so it needs more CFM to move the same volume of air as a wall hood. Most island hoods need 25 to 50 percent more CFM than a wall hood over the same cooktop. A 36-inch island cooktop might need 375 to 450 CFM instead of 300 CFM.

Downdraft hoods pull air down through or behind the cooktop. They're convenient for island layouts but less efficient than wall hoods because they work against rising heat and steam. Downdraft hoods typically need 400 to 600 CFM for a standard cooktop.

Noise and energy use at higher CFM

Higher CFM means more noise. A 150 CFM hood runs quietly at around 50 decibels (like a normal conversation). A 400 CFM hood at full speed can reach 70 to 80 decibels (like a vacuum cleaner or heavy traffic). If you're sensitive to noise, look for a hood with multiple speed settings so you can run it lower when you're not cooking heavily.

Higher CFM also uses more electricity. A 150 CFM hood uses roughly 30 to 50 watts. A 400 CFM hood uses 100 to 200 watts. Over a year, that difference adds up, especially if you run the hood constantly. Running the hood only when you're actually cooking saves energy and reduces noise.

Some hoods have dampers or backdraft preventers that close when the fan is off, stopping cold air from leaking back into your kitchen. Make sure any hood you buy has one — it prevents your furnace or water heater from being starved of air.

What to do if your kitchen is very tight or very open

A tightly sealed kitchen (new construction, well-weatherized homes) can create negative pressure when you run a high-CFM hood. Air gets pulled out faster than it can be replaced, which can cause your furnace, water heater, or fireplace to backdraft — pulling exhaust into the house instead of out the chimney. If your kitchen is very tight and you want a powerful hood, you may need to install a makeup air system that brings fresh air in while the hood pulls air out.

A very open kitchen (open to a living room or dining area) loses a lot of the hood's suction because air flows in from the open space instead of being pulled from the cooktop. You may need a higher CFM hood than the standard calculation suggests, or you may need to partially close off the kitchen with a partial wall or pocket doors when cooking heavily.

If you're unsure whether your kitchen setup will work with a high-CFM hood, talk to an HVAC technician before you buy. They can check your ductwork, measure your kitchen's air tightness, and recommend a CFM that won't cause problems.

Frequently Asked Questions

Can I use a hood that's too powerful for my stove?

Yes, but it may cause problems. A very powerful hood in a tight kitchen can create negative pressure and interfere with your furnace or water heater. It will also be noisier and use more energy than necessary. A hood rated 25 to 50 percent higher than your baseline is fine; one rated double your baseline may need a makeup air system.

What if my ductwork is really long or has lots of bends?

Buy a hood rated 25 to 50 percent higher than your baseline CFM to account for ductwork losses. If your ductwork is longer than 30 feet or has more than three elbows, talk to an HVAC technician — you may need a larger duct diameter or a more powerful hood than standard sizing suggests.

Is a recirculating hood (no ductwork) as good as a ducted hood?

No. A recirculating hood pulls air through a filter and blows it back into the kitchen instead of outside. It removes some grease and odor but leaves moisture and heat in the kitchen. A ducted hood is more effective. If you can't install ductwork, a recirculating hood is better than nothing, but it won't perform as well as a ducted system.

Do I need a makeup air system?

Only if your kitchen is very tightly sealed and you have a high-CFM hood (400 CFM or more). A makeup air system brings fresh air in while the hood pulls air out, preventing negative pressure. Ask an HVAC technician to assess your kitchen before you decide.

What CFM should I choose if I'm between two sizes?

Go with the higher CFM. A hood that's slightly oversized will work fine — you can run it on a lower speed setting to reduce noise and energy use. A hood that's undersized will struggle to clear smoke and steam, and you can't make it more powerful.