How Many CFM Do I Need for a Range Hood? (Gas vs Electric Chart)

1. The gas vs. electric CFM differential

A gas cooktop produces combustion byproducts (carbon monoxide, nitrogen dioxide, water vapor, fine particulate) that must be captured and exhausted by the range hood; an electric cooktop (induction or radiant) does not produce combustion byproducts, so the CFM requirement for an electric cooktop hood is driven by grease capture, smoke capture, and overall kitchen air exchange rather than by combustion safety. Because the gas cooktop hood is performing an additional safety function (capturing combustion byproducts), the CFM requirement is 40-100% higher than for an equivalent-size electric cooktop. The general rule from the ASHRAE residential ventilation guideline is 1 CFM of hood airflow per 100 Btu of burner output for gas cooktops, which translates to 400-600 CFM for a typical 30-inch residential gas cooktop and 200-300 CFM for a typical 30-inch electric cooktop. The electric cooktop baseline CFM (200-300 CFM for 30-inch) covers smoke, grease, and overall kitchen air exchange; the gas cooktop baseline CFM (400-600 CFM for 30-inch) covers the same plus combustion byproduct capture.

The differential matters for the hood selection. A hood rated at 280-450 CFM (such as the JILU A13 under-cabinet range hood) is the correct specification for a 24-30 inch electric cooktop or a 24-30 inch low-Btu (under 40,000 Btu) gas cooktop, but is undersized for a 30-inch standard residential gas cooktop (40,000-60,000 Btu combined burner output, which requires 400-600 CFM). For a 30-inch standard gas cooktop, the JILU wall-mounted cooker hood line provides the 400-700 CFM band; for a 36-inch gas cooktop (60,000-80,000 Btu, 600-800 CFM) and a 48-inch prosumer gas cooktop (80,000-120,000 Btu, 800-1,200 CFM), the JILU high-efficiency commercial kitchen exhaust hood line covers the upper CFM band. The substrate decision therefore is matched per cooktop type and size, not per the hood product line.

2. The Btu-to-CFM conversion rule

The single most useful sizing rule for range hoods over gas cooktops is CFM = (total Btu of all burners combined, peak output) / 100. For a typical 30-inch residential gas cooktop with 4 burners (each 10,000-15,000 Btu peak), the total Btu is 40,000-60,000 Btu, and the resulting CFM requirement is 400-600 CFM. The 1-CFM-per-100-Btu rule is the sizing floor (the minimum CFM that captures the combustion byproducts), not the sizing ceiling — actual CFM should be 20-30% above the floor to account for duct losses (elbows, length, transitions from the hood outlet to the exterior wall cap). On a 60,000 Btu cooktop with a 15-foot 6-inch duct run and two 90-degree elbows, the installed CFM at the cooktop is 100-150 CFM lower than the hood's zero-static-pressure rating, so a 480-780 CFM hood would be the correct specification. The JILU air volume and pressure guide provides the per-duct-diameter and per-elbow-count CFM loss table referenced in this section.

For an electric cooktop, the rule is different. The general sizing rule for electric cooktops is CFM = (kitchen floor area in square feet × 1.5) + 100. For a 100 square-foot kitchen, this gives 250 CFM; for a 150 square-foot kitchen, 325 CFM; for a 200 square-foot kitchen, 400 CFM. The rule is built on the assumption that the hood captures smoke, grease, and steam from a typical residential cooking session (saute, simmer, fry) within a typical residential kitchen volume, and the rule is independent of the cooktop Btu rating because the electric cooktop has no combustion safety envelope to satisfy. The ENERGY STAR ventilation fan certification covers the CFM-per-watt efficiency of residential range hoods within these sizing bands, and the JILU A13 under-cabinet line is designed to clear the ENERGY STAR threshold at the 280-450 CFM rating.

3. The duct length and CFM loss table

Duct length reduces CFM significantly. The loss is driven by friction (which scales with duct length and inversely with duct diameter) and by turbulence at fittings (which scales with the number of elbows and transitions). A 6-inch rigid metal duct run has a typical friction loss of 0.5-1.0 inches of water column per 100 linear feet at 400 CFM; an 8-inch duct run at the same CFM has a loss of 0.1-0.2 inches of water column per 100 linear feet; a 10-inch duct run at the same CFM has a loss of 0.05-0.1 inches of water column per 100 linear feet. Each 90-degree elbow adds the equivalent of 5-10 linear feet of straight duct; each 45-degree elbow adds the equivalent of 3-5 linear feet. The cumulative loss on a typical residential install (15-foot 6-inch duct with two 90-degree elbows) is 100-150 CFM at a 400 CFM hood rating.

The implication of the table is that a hood rated at 400 CFM at zero static pressure may deliver only 250-300 CFM at the cooktop after a 15-foot 6-inch duct run with two 90-degree elbows. The JILU air volume and pressure guide recommends the 8-inch duct upgrade when the duct run exceeds 12 linear feet or when more than two elbows are required; the upgrade recovers 50-100 CFM at the cooktop, which is typically the difference between undersized and correctly-sized airflow for a residential gas cooktop. The AHRI duct performance database provides equivalent CFM-loss tables for the broader HVAC duct specification, with the range hood use case covered in the residential ventilation fan category.

4. CFM vs sones (the noise consideration)

CFM (cubic feet per minute) measures how much air the hood moves; sones measure how loud the hood is at that airflow. A typical quiet residential range hood runs at 1-3 sones at low speed and 6-9 sones at high speed. The relationship between CFM and sones is non-linear: doubling the airflow typically increases the sound level by 6-9 sones (a 6-sone hood is roughly 4x louder than a 1.5-sone hood). The HVI certified ratings program certifies both CFM and sones for residential range hoods per the HVI-916 airflow procedure and the HVI-915 sound procedure. The Intertek laboratory runs the third-party CFM and sones test data that backs the HVI certified rating. The JILU A13 under-cabinet range hood is rated at 280-450 CFM at 3-7 sones depending on speed setting, which positions it in the mid-quiet residential category (comparable residential hoods typically run 1-4 sones at low speed and 5-9 sones at high speed).

The CFM-vs-sones trade-off is the central residential range hood selection decision for kitchens with adjacent living space. A buyer who selects the highest CFM hood often ends up with a hood that is too loud at full speed for residential use; the buyer who selects the lowest sones hood often ends up with a hood that is undersized for the cooktop. The JILU A13 line was designed to deliver a mid-quiet rating (3-7 sones) within the 280-450 CFM band, which positions it for open-plan residential kitchens where the hood is audible but not disruptive at normal cooking speed. For kitchens where silence is the priority, JILU recommends selecting a hood at the lower-CFM setting (200-300 CFM at 1.5-3 sones) and running the hood on the higher setting only for high-smoke or high-grease cooking; for kitchens where CFM is the priority, JILU recommends the wall-mounted cooker hood line (400-700 CFM) or the commercial kitchen exhaust hood line (900-1,800 CFM).

5. Makeup air and the 400-CFM threshold

In many jurisdictions, a residential range hood above 400 CFM requires makeup air to be introduced into the kitchen, to prevent depressurization of the home. The relevant codes are the IRC M1505 (International Residential Code, Section M1505 — Kitchen Ventilation) and the IMC Section 505 (International Mechanical Code — Commercial Kitchen Ventilation). When a 600 CFM or 900 CFM hood exhausts air from a tightly-sealed modern home, the resulting depressurization pulls backdrafts from the water heater flue, the furnace flue, and the fireplace, which is a carbon monoxide exposure risk. The makeup air requirement is satisfied by either a passive intake (a wall vent with motorized damper that opens when the hood is running) or an active makeup air unit (a small inline fan that introduces tempered outdoor air into the kitchen). The JILU North American kitchen range hood size standards and codes guide covers the makeup air sizing per the IRC M1505.4 and the equivalent Canadian National Building Code requirements.

The 400 CFM threshold means that the JILU A13 under-cabinet range hood at 280-450 CFM typically does NOT require a makeup air upgrade (most jurisdictions set the threshold at 400 CFM, so the A13 at the lower end of its CFM band falls below the threshold); a JILU wall-mounted cooker hood at 400-700 CFM MAY require a makeup air upgrade depending on the jurisdiction; a JILU commercial kitchen exhaust hood at 900-1,800 CFM ALWAYS requires a makeup air upgrade. The cost of the makeup air upgrade is typically USD 200-800 for a passive motorized damper or USD 800-2,500 for an active makeup air unit; the installation is paired with the hood installation in the same trade visit. The ENERGY STAR certification requires that residential hoods above 400 CFM ship with a factory-installed makeup air compatibility statement; the JILU A13 is below the 400 CFM threshold and is not required to ship with the statement.

6. CFM by cooktop size — the quick reference chart

The chart above combines the ASHRAE 1-CFM-per-100-Btu sizing rule, the ASHRAE 62.2 15-CFM-per-100-sq-ft baseline, the duct length CFM loss table from Section 3, and the JILU product line CFM ratings. The "JILU Model Match" column is the buyer-action column — the row that matches the buyer's cooktop type and size maps to the JILU product line that delivers the correct CFM at the cooktop after typical duct losses. The buyer who selects the JILU model from the matching row ends up with a correctly-sized hood; the buyer who selects a model from a different row ends up either with an undersized hood (combustion safety risk for gas) or an oversized hood (unnecessary cost and noise for electric). The JILU under-cabinet range hood line serves the 24-30 inch residential electric and low-Btu gas cooktop segment; the JILU wall-mounted range hood line serves the 30-36 inch standard gas cooktop segment; the JILU commercial kitchen exhaust hood serves the 48-inch prosumer gas and light-commercial segment.

7. FAQ — Gas vs Electric Range Hood CFM

1. How many CFM do I need for a range hood over a gas cooktop?

A gas cooktop requires roughly 1 CFM of hood airflow per 100 Btu of burner output. A typical 30-inch residential gas cooktop with 4 burners totalling 40,000-60,000 Btu requires 400-600 CFM; a typical 36-inch gas cooktop with 5 burners totalling 60,000-80,000 Btu requires 600-800 CFM; a typical 48-inch prosumer gas cooktop with 6 burners totalling 80,000-120,000 Btu requires 800-1,200 CFM; a 24-inch low-Btu gas cooktop under 30,000 Btu combined requires 200-300 CFM. The JILU A13 under-cabinet range hood serves the lower CFM band (280-450 CFM) and pairs with 24-30 inch electric or low-Btu gas cooktops; the JILU wall-mounted range hood line serves the standard 30-inch gas cooktop; the JILU commercial kitchen exhaust hood line serves the 36-inch and 48-inch gas cooktops. The sizing rule is a sizing floor (CFM = total Btu / 100), not a sizing ceiling — actual CFM should be 20-30% above the floor to cover duct losses.

2. How many CFM for an electric cooktop range hood?

An electric cooktop (induction or radiant) does not produce combustion byproducts, so the CFM requirement is lower than for gas. The general rule is 200-300 CFM for a 30-inch electric cooktop, 300-450 CFM for a 36-inch electric cooktop, and 400-600 CFM for a 48-inch electric cooktop. The ASHRAE 62.2 residential ventilation standard requires 15 CFM per 100 square feet of kitchen floor area as a baseline regardless of cooktop type; an additional 200-600 CFM of cooktop-targeted exhaust is added when the hood is operating on top of the baseline. The ENERGY STAR ventilation fan certification covers the CFM-per-watt efficiency at these sizing bands; the JILU A13 under-cabinet line is designed to clear the ENERGY STAR threshold at 280-450 CFM.

3. Does duct length reduce CFM, and by how much?

Yes, duct length reduces CFM significantly. Each 90-degree elbow reduces airflow by the equivalent of 5-10 linear feet of straight duct; each 45-degree elbow reduces airflow by the equivalent of 3-5 linear feet; every 10-15 linear feet of straight rigid metal duct reduces airflow by 50-100 CFM depending on duct diameter. A 6-inch duct run of 20 feet with two 90-degree elbows typically loses 100-150 CFM relative to the hood's rated CFM. The JILU A13 under-cabinet range hood is rated at 280-450 CFM at zero static pressure, but the installed CFM at the cooktop may be 200-380 CFM after a typical 15-foot 6-inch duct run. An 8-inch duct typically adds 30-50% less static loss than a 6-inch duct at the same CFM. The JILU air volume and pressure guide provides the per-duct-diameter and per-elbow-count CFM loss table.

4. What is the difference between CFM and sones on a range hood?

CFM measures airflow volume; sones measure the sound the hood produces at a given airflow. A typical quiet residential range hood runs at 1-4 sones at low speed and 6-9 sones at high speed. The HVI certifies both CFM and sones ratings per the HVI-916 airflow and HVI-915 sound performance procedures. The JILU A13 is rated at 280-450 CFM and 3-7 sones depending on speed setting, positioning it in the mid-quiet residential category. A 6-sone hood is roughly 4x louder than a 1.5-sone hood; the perceived difference is typically the deciding factor on residential hood selection.

5. Do I need makeup air if my range hood exceeds 400 CFM?

Yes, in many jurisdictions. The IRC M1505 and the IMC Section 505 require makeup air to be introduced when the range hood exceeds 400 CFM, to prevent depressurization of the home. Without makeup air, the hood pulls backdrafts from the water heater, the furnace, and the fireplace, which is a carbon monoxide hazard. The JILU commercial kitchen exhaust hood product line pairs with the makeup air intake duct sizing covered in the JILU North American kitchen range hood size standards guide; for residential hoods above 400 CFM, JILU recommends the IRC M1505.4 makeup air damper or an equivalent motorized damper.

6. How do I convert BTU to CFM?

The general rule is CFM = (total Btu of all burners combined) / 100 for gas cooktops. For a 30-inch gas cooktop with 4 burners, the typical Btu range is 40,000-60,000 Btu (10,000-15,000 Btu per burner at peak), and the resulting CFM requirement is 400-600 CFM. The rule of 1 CFM per 100 Btu is a sizing floor, not a sizing ceiling — actual CFM should be 20-30% above the floor to account for duct losses. For electric cooktops, the rule is CFM = (kitchen floor area in square feet × 1.5) + 100, which gives 250-450 CFM for a 100-200 square-foot kitchen.

7. Do downdraft cooktops need CFM the same way as overhead hoods?

No. Downdraft cooktops (pop-up ventilation built into the cooktop surface) typically require higher CFM than overhead hoods to achieve the same capture rate, because downdraft capture is less efficient than overhead capture. A 30-inch downdraft typically requires 600-1,000 CFM compared to 350-600 CFM for a comparable 30-inch overhead hood, per the ASHRAE 62.2 residential ventilation guideline and the HVI downdraft capture performance data. The JILU product line is focused on overhead hoods (under-cabinet / wall-mounted / island / commercial) rather than downdraft.

About the author

Mr. Zheng | Technical Director
Mr. Zheng has spent more than 30 years working on kitchen ventilation, stainless steel fabrication, and performance-focused exhaust solutions for demanding cooking environments. His practical experience covers airflow design, durability planning, and the details that make outdoor BBQ hoods last in real-world conditions.
Experience: 30+ years in kitchen ventilation, stainless steel fabrication, airflow design, durability planning, and commercial exhaust solutions.
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