300 vs 400 vs 600 CFM Range Hood: How Much Do You Need?

Most kitchens need somewhere between 300 and 600 CFM. A typical 30” electric or induction range is well served by about 300 CFM, most standard gas ranges land near 400 CFM, and 600 CFM is for high-output gas, wide cooktops and island hoods. The right number for you depends on your cooktop, hood type and room, and the range hood CFM calculator works it out in about a minute. This page explains what goes into that number and what changes as you move up.

300 vs 400 vs 600 CFM at a glance

Noise figures are typical ranges on the highest speed; lower speeds are much quieter. Always compare HVI-certified sone ratings for the specific hood.

The rules of thumb, with worked examples

There is no single correct formula. Run each rule that applies and use the biggest result. The code minimum, 100 CFM intermittent under IRC M1505.4.4, is a floor, not a target.

Gas: 100 CFM per 10,000 BTU

Add up the maximum BTU rating of every burner, then divide by 100.

Example: a 30” gas range with burners of 18,000, 12,000, 9,500 and 5,000 BTU totals 44,500 BTU. That points to about 445 CFM, so a 400 CFM hood is slightly short and a 450–500 CFM hood is a better match.

Your burner ratings are on the range’s rating plate (often inside the oven door or storage drawer) or in the manual.

Electric and induction: 10 CFM per inch of width

Example: a 30” electric or induction cooktop needs about 300 CFM. A 36” cooktop needs about 360 CFM.

Induction produces less waste heat than gas, but the food still makes the same smoke, grease and steam, so do not undersize for induction.

By hood type: CFM per foot of cooktop width

• Wall-mount and under-cabinet: about 100 CFM per linear foot. A 36” (3-foot) range → about 300 CFM.
• Island: about 150 CFM per linear foot because open-air hoods lose smoke to cross-drafts. A 36” island cooktop → about 450 CFM. See island vs wall-mount hoods.

By room: 15 air changes per hour

Multiply kitchen length × width × ceiling height for volume in cubic feet, multiply by 15 air changes per hour, then divide by 60.

Example: a 12’ × 14’ kitchen with 9’ ceilings is 1,512 cubic feet. 1,512 × 15 ÷ 60 = about 378 CFM. In open-plan homes, include the part of the living space that shares the kitchen air, which pushes the number up.

Putting it together

Take one kitchen: a 36” gas range with 60,000 BTU total, under a wall-mount hood, in a 14’ × 16’ kitchen with 9’ ceilings.

• Gas rule: 60,000 ÷ 100 = 600 CFM
• Wall hood rule: 3 feet × 100 = 300 CFM
• Room rule: 2,016 cu ft × 15 ÷ 60 = 504 CFM

The largest is 600 CFM, so this kitchen belongs in the 600 CFM class, with the makeup air and duct size that come with it. The CFM calculator runs all of these rules at once and also suggests hood width and duct size.

The 400 CFM makeup air threshold

The International Residential Code (IRC) 2021, Section M1503.6, requires makeup air for kitchen exhaust systems able to exhaust more than 400 CFM. Makeup air replaces the air your hood pushes outside, usually through a ducted inlet with a motorized damper that opens when the hood runs, sometimes with a heater.

Why it matters:

• Performance. In a tight house, a big hood cannot pull air it cannot replace. A 600 CFM hood without makeup air may perform like a much smaller one.
• Safety. Negative pressure can pull exhaust gases back down the flue of a gas water heater, furnace or fireplace.
• Cost. Makeup air systems often add a typical $1,000–$3,000+ to the project.

Note the wording: “able to exhaust,” so a hood rated for 600 CFM on high counts even if you usually run it on low. This is why many hoods are sold at exactly 400 CFM. Local codes vary and are adopted with amendments, so check with your local building department before choosing a hood above 400 CFM.

Noise at each level

Noise is rated in sones. About 1 sone is a quiet refrigerator; 3–4 sones is normal conversation.

• 300 CFM: often comfortable to talk over on high, and near-silent on low. Small under-cabinet blowers can still be buzzy.
• 400 CFM: noticeable on high, still manageable for most people.
• 600 CFM: commonly 6–9 sones on high, loud enough to interrupt conversation. Most people run these on low or medium and use high only for searing and frying.

Two things reduce noise at any CFM: larger duct than the minimum and fewer elbows. Some high-CFM hoods use an inline or exterior blower to move the motor away from the kitchen. A hood that is too loud on medium is often a sign of undersized or restrictive ductwork, not only the fan.

Duct size at each level

• 300 CFM: 3¼” × 10” rectangular (common on low-CFM under-cabinet hoods) or 6” round.
• 400 CFM: 6” round is typical.
• 600 CFM: 7–8” round.
• Above 600 CFM: 8–10” round.

Never reduce duct size below the hood’s collar. Use smooth rigid metal duct, keep the run under about 30 equivalent feet, and count each 90° elbow as roughly 10–15 feet of straight duct. A 600 CFM hood on an undersized, twisting duct can move less air than a well-ducted 400 CFM hood, and it will be louder doing it. If your current hood feels weak, range hood not venting covers what to check before upgrading.

Cost

Typical US ranges for the hood alone: $100–$600 at around 300 CFM, $200–$1,000 at around 400 CFM, and $400–$2,000+ at 600 CFM. The bigger cost jumps come from what surrounds the hood: upsizing a 6” duct to 8”, cutting a larger wall or roof hole, and adding makeup air. Moving from 400 to 600 CFM can easily add more to the project than the price difference between the two hoods.

Which should you choose?

Choose about 300 CFM if:

• You have a 30” electric or induction range.
• You mostly boil, simmer, bake and sauté.
• You have an existing 3¼” × 10” or 6” duct and want a like-for-like swap.

Choose about 400 CFM if:

• You have a standard gas range around 30,000–40,000 BTU total.
• You have a 36” electric or induction cooktop, or cook at high heat a few times a week.
• You want strong performance while staying at the makeup air threshold.

Choose about 600 CFM if:

• Your gas cooktop totals 50,000–60,000 BTU or more.
• You have an island cooktop 36” or wider.
• You sear, stir-fry or deep-fry often.
• You can run 7–8” duct and budget for makeup air.

If you are between two levels, a hood with a good low speed and HVI-rated sones will serve you better than a hood with the highest possible CFM. See gas vs electric stove ventilation for how fuel type changes the answer.

What to look for when buying

• A target CFM from the CFM calculator, using the largest rule that applies.
• HVI-certified CFM, since certified airflow is measured under standard conditions.
• HVI-certified sones at low and high speed.
• At least three fan speeds, with a quiet low setting for everyday use.
• Duct collar size that matches the CFM and your existing duct.
• A hood width at least equal to your cooktop.
• If over 400 CFM: a makeup air plan and a check with your local building department.
• Washable baffle or mesh filters sized for the airflow.
• A backdraft damper at the collar or exterior cap.

The bottom line

More CFM is not automatically better. Match the hood to your cooktop and room, respect the 400 CFM makeup air line, and give the fan duct big enough to breathe. Put your own cooktop and kitchen size into the CFM calculator to find your number.