How to Size Range Hood CFM

On this page (10 sections)

1. How do you size a range hood CFM in five steps?
2. How wide should the range hood be for the stove?
3. How many CFM do you need for each burner output?
4. How do duct length and duct size change the CFM you need?
5. What CFM should a ductless or recirculating hood have?
6. How does noise track with CFM?
7. What else changes the CFM you need?
8. Which hoods fit a correctly sized 30-inch kitchen?
9. How do you confirm the CFM before you buy?
10. The bottom line on how to size range hood CFM

Sizing a range hood CFM starts with two facts: the width of your cooktop and the output of your burners. Pick a hood at least as wide as the stove, then allow about 100 CFM for every 10,000 BTU, and add margin for the duct run.

This guide walks through how to size range hood CFM step by step so the blower clears smoke without wasting air or creating noise.

The goal is not the biggest number on the box. A correctly sized hood moves enough air for your cooking, fits the cabinets you have, and stays quiet on everyday settings.

Read on for the numbers to use and how each choice changes the final figure.

How do you size a range hood CFM in five steps?

Size a range hood by matching width first, then setting airflow from burner output and the duct path. The five steps below take about ten minutes with your stove's spec sheet and a tape measure.

1. Measure the cooktop width. A 30-inch stove takes a 30-inch hood, and a 36-inch stove takes a 36-inch hood.
2. Add up the BTU ratings of the burners. Use the highest single burner if your stove runs one big pot at a time.
3. Apply the CFM rule: about 100 CFM per 10,000 BTU. Round up to the next blower size you can buy.
4. Adjust for the duct run. Long runs, narrow ducts and sharp elbows cost performance, so allow extra.
5. Check local code. Many areas cap residential kitchen exhaust near 400 CFM without make-up air.

Keep your figures on one page as you go. The width and the BTU total drive most of the decision, and the duct path decides whether the blower you choose can deliver its rated airflow.

Our what size range hood do I need guide covers the width question in more detail.

Once you have a CFM number, compare it against the blowers sold in the size you need. A hood that is too small for the burner leaves grease on the cabinets, while an oversized one adds noise and cost without cleaning the air any better.

Rule: set width and burner output before you look at blower sizes. A big CFM number on a hood that is too narrow or behind a bad duct will not clear your smoke.

How wide should the range hood be for the stove?

The hood should be as wide as the cooktop, and a little wider is better. Match the stove's width in inches so the hood's capture area sits over every burner.

Width matters more than CFM for everyday capture. A narrow hood pulls smoke past its edges, and no blower size fixes that.

These widths cover most homes:

• 24 inches suits compact apartments and two-burner cooktops.
• 30 inches is the standard for most gas and electric ranges.
• 36 inches fits larger ranges and pro-style cooktops.
• 42 to 48 inches covers wide pro ranges and island setups.

A 36-inch hood over a 30-inch range captures more spillover, but only if your cabinets and duct allow it. Measure the space under the cabinet and the distance to the nearest wall before you buy.

Most under-cabinet hoods mount 18 to 24 inches above gas cooking surfaces and 24 to 30 inches above electric. Our how many CFM range hood do I need post pairs width with airflow for specific stove types.

Rule: never buy a hood narrower than the cooktop. A 30-inch stove needs at least a 30-inch hood, even if the blower seems strong enough on paper.

How many CFM do you need for each burner output?

Allow 100 CFM per 10,000 BTU of gas burner output. That is 1 CFM for every 100 BTU, and it is the starting point most sizing guides use.

Gas burners are rated in BTU, and the figure you need is the total for the burners you use together. A typical 30-inch gas range has four burners around 9,000 to 12,000 BTU each.

At 15,000 BTU you need about 150 CFM, and a stove with four 12,000 BTU burners totals 48,000 BTU for about 480 CFM if all run at once.

Electric and induction cooktops are rated in watts. The conversion is rough, but 1,000 watts is close to 3,400 BTU, so a 3,000-watt burner lands near 100 CFM.

Use the element you cook on most and add the others if you run several at once.

Use the highest burner when you cook one big pot at a time, since that burner creates most of the smoke and grease. Use the total when you often run several burners together.

This is where many buyers overshoot or undershoot, and the what CFM should a range hood have guide breaks down the figures by stove type.

Rule: base CFM on the burner output you actually cook with. A single strong burner sets the floor, and running several burners together sets the ceiling.

How do duct length and duct size change the CFM you need?

A long or narrow duct run slows airflow and costs you real CFM at the hood. Every extra foot of duct and every elbow adds resistance, so the rated blower figure and the delivered airflow are not the same number.

A short run straight out the back of the hood moves close to the rated CFM, while a run that crosses the kitchen and turns twice delivers less. Round rigid duct in 6-inch or 7-inch size carries airflow well, and flexible duct loses more than smooth pipe.

A 4-inch duct chokes a blower rated for 400 CFM and up, so match the duct to the hood's outlet. Most 30-inch hoods list a 6-inch round or 3.25 x 10-inch rectangular outlet.

Duct bends are the third factor. Two 90-degree elbows cut airflow more than one gentle sweep, so plan the shortest, straightest path you can.

If the run is long or bendy, add 10 to 20 percent to your CFM figure before you buy. A model with a 7-inch round outlet also flows more than a 6-inch one at the same blower rating.

Our is 400 CFM enough for range hood post covers what a typical mid-range blower delivers in real kitchens.

Rule: if the duct run is long, narrow or has several bends, add margin to the CFM figure. A strong blower behind a bad duct underperforms a modest one with a clean run.

What CFM should a ductless or recirculating hood have?

Ductless hoods recirculate air through a filter and return it to the kitchen, so they cannot move as much air as a ducted model. Their CFM figure describes the blower, not how much air leaves the room.

A ductless hood still needs enough airflow to pull smoke and grease through the filter. Aim for the same burner-based figure as a ducted hood, but expect less capture because the filtered air returns to the room.

Charcoal filters trap odors and grease, and they need replacing more often in heavy use. The width rule stays the same: a ductless hood should be as wide as the cooktop.

Our best ductless range hoods roundup covers models built for recirculation.

Rule: choose a ducted hood when you can. If ducting is impossible, size a ductless hood by width and burner output and plan to replace the charcoal filter on schedule.

How does noise track with CFM?

Higher CFM usually means more noise, and the figure that matters is sones at the speed you actually use. A hood rated at 1.5 sones on low can climb past 5 sones on high, so a strong blower can be loud when it works hard.

Sones are a linear scale. A hood at 2 sones is twice as loud as one at 1 sone, and 4 sones is twice as loud as 2.

Most people notice a jump above about 4 sones in a normal kitchen conversation. A larger blower turning slowly can move the same air more quietly than a small one spinning fast, which is why a 375 CFM hood and a 950 CFM model can both exist.

Read the sone figure at each speed. Variable-speed models let you run low for everyday cooking and boost only when needed.

For a closer look at how sone ratings translate to everyday noise, our range hood noise guide walks through the scale.

Rule: buy the lowest sone rating at the CFM you need. A hood that clears smoke quietly on medium beats one that only works on its loudest setting.

What else changes the CFM you need?

Stove type, hood height and cooking style all shift the figure. A gas pro-style range or wok burner needs more airflow than a standard electric cooktop, and a hood mounted higher captures less unless the blower is stronger.

A hood set at the top of its height range sits farther from the smoke, so it needs a little more CFM to capture the same plume. Cooking style counts too.

Everyday simmering needs less airflow than searing, deep frying or wok cooking. If you cook with high heat and oil often, aim toward the top of your CFM range rather than the minimum.

A very tight kitchen also needs make-up air when the hood runs hard, or the blower fights a pressure drop. That is another reason local codes cap high-CFM hoods.

Under-cabinet, wall and island hoods capture differently at the same width, and our range hood buying guide compares the layouts.

Rule: size for your heaviest cooking and the height you will install. If you sear or fry often, choose the next blower size up.

Which hoods fit a correctly sized 30-inch kitchen?

These three 30-inch under-cabinet hoods cover a range of CFM and features for a typical stove. Match each to the burner output and duct path you worked out above.

Broan-NuTone BCSQ130SS Glacier 30 Inch: steady everyday airflow

The Broan-NuTone Glacier suits a standard 30-inch gas or electric range with typical burners. Broan-NuTone rates it at a maximum 375 CFM with a three-speed push button, and its Captur system is designed to pull smoke and odors through a forward-centered inlet.

Its 30-inch width matches a standard range, and the unit measures 19.6 inches deep by 6 inches high. The dual open mesh grease filters are dishwasher safe, and a single LED module lights the cooking area.

It installs as a 3.25 x 10-inch ducted opening or as a non-ducted recirculating hood with a filter sold separately. Broan-NuTone says the blower runs at 5.5 sones on high and 1.5 sones on low.

That spread is worth noting: the low setting is quiet enough for everyday cooking, and the high setting clears a sear.

Pick it for a standard 30-inch stove where the burner total lands near 375 CFM and you want a simple push button control. Skip it if your burners run well above that figure or your duct run is long and bendy.

Hauslane UC-PS38 30 Inch Auto Clean: high output for heavy cooking

The Hauslane UC-PS38 suits home cooks who sear, fry or run several burners together. It moves up to 950 CFM through dual motors, with a six-speed touch control that lets you dial down to a quiet setting for everyday meals.

The 30-inch width fits a standard range, and the panel design is meant to capture smoke from the front burners as well as the back. It has a steam clean cycle that turns water into steam to loosen grease, then sprays water to rinse.

A stainless steel oil tray and water tray are included, along with a 6-inch round exhaust adapter. The hood uses GU10 LED bulbs you can swap from a local hardware store.

Hauslane backs the motors with a lifetime warranty and the unit with a two-year limited warranty. Noise is rated at 67 dB, so expect a noticeable hum when it runs on high.

Pick it for heavy cooking where the burner total is high and you want the extra airflow headroom. Skip it if your stove is modest and your priority is a quiet everyday hood, since the extra capacity costs noise and budget.

COSMO COS-QS75 Haven 30 Inch: mid-range airflow with touch controls

The COSMO Haven suits a 30-inch range that needs a mid-range blower with modern controls. It is rated at 500 CFM with four fan speeds, twin centrifugal motors and a backlit touchscreen, plus a wireless remote.

The stainless steel ARC-FLOW permanent filters are dishwasher safe, and the unit measures 30 inches wide, 22 inches deep and 10 inches high. It vents outside through a top 7.5-inch round duct.

COSMO rates noise as low as 40 dB on the lowest speed with rigid ducting under optimal conditions. A carbon filter kit sold separately converts it to ductless.

The 500 CFM rating sits between the two hoods above. That makes it a reasonable fit for a 30-inch range with moderate burners and a duct run that is not too long.

The 1.5-watt LEDs save energy and the remote lets you change speed without reaching up.

Pick it for a balanced 30-inch setup where you want touch controls and a blower in the middle of the range. Skip it if your burner total is high or your duct path is long enough to need the extra margin.

How do you confirm the CFM before you buy?

Confirm your figure by checking three things: the burner output, the duct path and the local code. Write each down and compare against the hood's rated CFM at its highest speed.

Start with the burner total. Add the BTU of the burners you run together, or use the highest single burner, and apply the 100 CFM per 10,000 BTU rule.

Round up to the next blower size you can buy. Next, check the duct.

Measure the run length, count the bends and note the duct diameter. If the run is long or narrow, add 10 to 20 percent.

A hood rated at 375 CFM behind a long 4-inch run delivers far less than its number. Then check the code.

Many areas limit residential kitchen exhaust near 400 CFM without make-up air. A high-CFM hood may need a make-up air system or a damper, and your local building office can confirm the rule.

Finally, compare the sone rating at the speed you will use most. A hood that clears smoke on medium at a low sone figure will feel better every day than one that only works on high.

Our range hood CFM calculator guide shows how the numbers stack up for different stoves.

Rule: buy the hood whose rated CFM sits at or above your figure, whose duct matches your run, and whose sone rating is acceptable at the speed you will use. If two hoods tie, choose the quieter one.

The bottom line on how to size range hood CFM

The simplest way to size range hood CFM is width first, burner output second, duct path third. Pick a hood as wide as the cooktop, allow 100 CFM per 10,000 BTU, add margin for a long or bendy duct, and check your local code before you buy a high-CFM model.

For a standard 30-inch gas range, a hood in the 375 to 500 CFM range covers most cooking. The Broan-NuTone Glacier is the easy fit for everyday burners, the COSMO Haven adds touch controls and a mid-range blower, and the Hauslane UC-PS38 brings the airflow headroom for heavy cooking.

Pick the one whose CFM, duct outlet and noise level match your kitchen.

If you are still deciding on width or stove type, read our what size range hood do I need guide before you order. And if you are weighing a mid-range blower, our is 400 CFM enough for range hood post helps you judge whether 400 CFM clears your burners.

Frequently asked questions

How many CFM do I need for a 30-inch gas range?

Allow about 100 CFM per 10,000 BTU of your highest burner and size the hood as wide as the cooktop. A 30-inch gas stove with a 15,000 BTU burner calls for around 150 CFM at minimum, then more for duct runs and bends.

Is a 400 CFM range hood enough?

400 CFM covers most 30-inch gas stoves, since the burner rule lands near 150 to 300 CFM for typical outputs. Go higher if your duct run is long, has several elbows, or your stove has burners well above 30,000 BTU total.

Should the range hood be wider than the stove?

It should be at least as wide as the cooktop. Going one size wider, such as 36 inches over a 30-inch range, captures more spillover steam and smoke, but only if your cabinet and duct layout allow it.

Do I need more CFM for a high-output gas burner?

Yes. CFM should follow your highest burner output, not the average, because a single powerful burner creates most of the smoke and grease.

Match the blower to that burner, then confirm the duct can move that much air.

What is the maximum CFM a home exhaust can use?

Many local codes cap kitchen exhaust around 400 CFM unless the hood has a make-up air system. Check your local code before buying a high-CFM hood, because a larger blower can create backdraft and pressure problems.