How to Choose the Right Kitchen Fan Size: 1 Minute to Master Kitchen Fan Sizing for Every Home

I’ve sized kitchen ventilation systems for homes ranging from compact city apartments to open-plan chef-grade spaces. The right fan size isn’t just a number—it’s a balance of capture efficiency, airflow (CFM), duct performance, and acoustic comfort. Done well, you’ll keep grease, heat, and odors under control without elevating noise or energy bills.

Ventilation is about removing contaminants and heat at the source. WELL v2 highlights source control and ventilation as foundational to indoor air quality, with cooking recognized as a major particulate source. Steelcase research has shown that noise above 45–50 dBA begins to erode task performance; in residential kitchens, that translates to choosing a fan that achieves required CFM at lower speeds to keep sound pressure manageable. These datapoints anchor an approach that prioritizes both performance and comfort. You can explore WELL v2’s indoor air quality guidance at WELL v2.

Most homeowners focus only on the fan’s CFM rating. In practice, capture area (hood width and depth), mounting height, and duct resistance are equally decisive. A well-sized hood that covers the cooktop can capture rising plume efficiently, meaning you may not need a dramatically higher CFM. The goal: right-sized airflow, effective capture, and ducting that actually delivers that airflow to the exterior.

Understand the Core Sizing Formula

There are two widely used baselines:

- Electric/induction cooktops: 100 CFM per linear foot of hood width. A 30-inch (2.5 ft) hood targets ~250 CFM when well-captured.

- Gas ranges: 1 CFM per 100 BTU of total burner output. A 50,000 BTU range suggests ~500 CFM. If you frequently sear or use high-output burners, plan higher.

For island hoods, add 10–20% due to greater plume dispersion. For shallow hoods with limited depth, consider +15% to offset reduced capture volume.

Match Hood Size to Cooktop

As a rule, size the hood equal to or 3 inches wider than the cooktop on each side for wall installations. Depth should be 20–24 inches for pro-style ranges, 18–20 inches for standard residential units. Island hoods benefit from greater depth and side capture because there’s no back wall to help contain the plume.

If you’re mapping layouts or comparing clearances in a remodel, a room layout tool can help visualize hood width, depth, and mounting height against cabinetry and sightlines: room design visualization tool.

CFM Tiers That Work in Real Kitchens

- 200–300 CFM: Light cooking, electric/induction, apartments with minimal frying.

- 300–450 CFM: Typical home use, mixed methods, occasional searing.

- 450–600 CFM: Gas ranges ~45k–60k BTU, regular wok searing or heavy frying.

- 600–900+ CFM: Pro-style ranges ≥70k BTU, frequent high-heat cooking. Plan make-up air and robust duct.

Ducting: The Hidden Performance Variable

Duct size, length, and geometry determine whether your selected CFM reaches the exterior. For 250–400 CFM, 6-inch round duct is a practical minimum. For 400–600 CFM, step up to 7-inch; 600–900+ CFM usually needs 8-inch duct. Limit elbows; each 90° elbow can add the equivalent of 5–10 feet of straight duct resistance depending on radius. Smooth-walled metal ducting outperforms flex duct by a wide margin.

Keep the run as short and straight as possible, vent outdoors (never into the attic), and use a roof or wall cap sized to the duct. Poor caps can add backpressure and noise.

Mounting Height and Capture Efficiency

Mount wall hoods about 24–30 inches above the cooktop; island hoods often sit at 30–36 inches due to sightlines. Higher mounting requires either a deeper hood or more CFM to maintain capture. If I have a shallow hood mounted high, I add ~15–20% CFM to compensate or specify a design with greater baffle coverage.

Noise, Acoustics, and Usability

Look at sones or dB ratings at working speeds, not just max. A fan that achieves your needed CFM at medium speed will sound quieter and be used more consistently. Steelcase research on cognitive performance around noise supports selecting systems that keep sound levels moderate—think under ~50 dBA in open-plan kitchens adjacent to living spaces when possible. Remote (in-line or external) blowers can dramatically reduce perceived noise at the cooktop.

Grease Filtration and Maintenance

Baffle filters have lower static resistance and better grease collection than mesh at higher CFM; they’re also easier to clean. Plan filter access without contortions. Regular cleaning preserves airflow and lowers fire risk.

Make-Up Air: Don’t Skip It

At or above ~400–600 CFM, many jurisdictions require make-up air to balance pressure and maintain combustion safety for gas appliances elsewhere in the home. Even when not mandated, providing tempered make-up air prevents backdrafting and helps the fan maintain rated performance.

Special Cases: Induction vs. Gas, Islands vs. Walls

Induction generates less convective heat than gas, so capture is often easier and lower CFM suffices when hood geometry is sound. Island cooktops, however, disperse plumes more freely; plan wider, deeper hoods and +10–20% CFM.

Step-by-Step Sizing Workflow

1) Confirm cooktop type and total BTU (gas) or width (electric/induction).

2) Choose hood width equal to or +6 inches wider than cooktop for islands; +3 inches each side for wall applications.

3) Set depth to 18–24 inches depending on range type.

4) Calculate baseline CFM (100 CFM/ft for electric; 1 CFM per 100 BTU for gas), then adjust +10–20% for islands or high mounting.

5) Size duct: 6–8 inches round based on CFM; minimize elbows and use smooth metal.

6) Verify sound ratings and consider remote blowers for lower noise.

7) Plan make-up air at ≥400–600 CFM.

8) Confirm local code and installation clearances.

Design Details That Improve Everyday Use

- Controls at the front edge or underside: quick access without reaching over heat.

- LED task lighting with 3000–3500K color temperature for warm-neutral clarity and low glare.

- Capture lip and full-width baffles for better plume containment.

- Timers and auto run-on for post-cook clearing.

Common Pitfalls I See

- Oversizing CFM without fixing ducting—results in noise and minimal real capture gains.

- Under-sizing hood depth—plumes roll past the front edge, especially on front burners.

- Ignoring make-up air—causes door slamming, drafts, and potential HVAC or combustion issues.

- Venting into attic—moisture and grease damage; always exhaust outdoors.

FAQ

Q1: What CFM do I need for a 36-inch gas range at 60,000 BTU?

A: Start at ~600 CFM (1 CFM per 100 BTU). If the hood is an island or mounted higher than 30 inches, add 10–20%.

Q2: Is a 300 CFM hood enough for induction?

A: Often yes for a 30-inch induction cooktop, provided the hood is at least as wide, with 18–20 inches depth and proper ducting.

Q3: How loud is a typical range hood?

A: Many hoods run 1.5–5 sones depending on speed. Choose a model that meets your target CFM at mid speed, or consider an in-line/external blower to reduce perceived noise.

Q4: Do recirculating (ductless) hoods work?

A: They can capture some odors with carbon filters, but they won’t remove heat or moisture. For regular frying or gas cooking, vented hoods are far more effective.

Q5: What duct size is best for 600 CFM?

A: Use 7–8-inch round duct, minimize elbows, and select a cap sized for the duct to avoid backpressure.

Q6: How high should I mount the hood?

A: Generally 24–30 inches above the cooktop for wall hoods, 30–36 inches for islands. Higher mounting needs deeper hoods or more CFM.

Q7: Do I need make-up air?

A: Above ~400–600 CFM, many codes require it. It stabilizes pressure and helps maintain rated airflow, especially in tight homes.

Q8: Baffle vs. mesh filters—what’s better?

A: Baffles handle higher grease loads with lower resistance and are easier to clean. Mesh can clog faster at higher CFM.

Q9: Can lighting color temperature affect cooking visibility?

A: Yes. Around 3000–3500K delivers warm-neutral clarity with good color rendering and lower glare for task work.

Q10: What if I have a very long duct run?

A: Increase duct diameter, reduce elbows, and consider a more powerful blower or an in-line booster to overcome static pressure.