Maintained by the BuildSolver engineering team · Updated
Calculator · Kitchen range hood
Range hood CFM calculator
Enter the range and the kitchen, and this calculator compares the HVI rate per linear foot with the IRC and ASHRAE 62.2 code minimum, then checks the result against the IRC makeup air threshold of 400 CFM.
- Type the cooking surface width, pick wall or island, and enter the total gas burner input, or 0 for electric.
- Enter the kitchen dimensions, whether it is open or enclosed, and whether a fuel-burning appliance sits inside the air barrier.
- The result shows the HVI rate, the code minimum and the makeup air check, and takes the larger of the two airflows.
Example result for the default inputs
30 in cooking surface against a wall, electric or induction, 14 ft x 12 ft open kitchen with a 9 ft ceiling.
Recommended hood airflow
250 CFM
Code minimum, vented hood
100 CFM
| Hood length, matched to the cooking surface | 2.5 ft |
|---|---|
| HVI recommended, against a wall (100 CFM per linear ft) | 250 CFM |
| HVI minimum, against a wall (40 CFM per linear ft) | 100 CFM |
| Gas input rule of thumb, reference only (1 CFM per 100 BTU/h, not an HVI or code number, does not change the result) | Not used, no gas input entered |
| Code minimum, vented range hood, intermittent (2021 IRC Table M1505.4.4 and ASHRAE 62.2-2013 Addendum c) | 100 CFM |
| Code minimum, continuous kitchen exhaust (2021 IRC Table M1505.4.4) | 25 CFM |
| Kitchen volume | 1,512 cu ft |
| ASHRAE 62.2-2013 Addendum c continuous kitchen exhaust (5 ACH of kitchen volume, enclosed kitchens only) | Not permitted for an open kitchen, use demand-controlled exhaust |
| ASHRAE 62.2-2013 Addendum c minimum for a kitchen fan that is not a hood, including downdraft | 300 CFM |
| Makeup air (2021 IRC M1503.6, over 400 CFM) | Not triggered, the recommended airflow is at or under 400 CFM. A hood capable of more still triggers it. |
For estimation purposes only. Consult a licensed engineer for final designs.
Free without signup, 3 questions a day
How the recommended hood airflow is calculated
Each method runs on its own row. The recommended hood airflow is the larger of the HVI rate and the code minimum for a vented hood, the two sourced numbers. A gas input rule of thumb shows as a reference row. It never moves the result. Makeup air is checked against the exact recommended number before it is rounded up.
- HVI rate per linear foot
CFM = cooking surface width (in) / 12 x 100 against a wall, or x 150 over an islandHVI recommends 100 CFM per linear foot of range against a wall and 150 over an island, with minimums of 40 and 50. The hood length is taken as the cooking surface width, since HVI says hood width should match the range.- Gas input rule of thumb
CFM = total burner input (BTU/h) / 100A common field rule for gas ranges. HVI, the IRC and ASHRAE 62.2 do not state it, so the calculator shows it for reference only. It does not change the recommended airflow or the makeup air check.- Code minimum, vented hood
100 CFM intermittent, or 25 CFM continuous under the IRC2021 IRC Table M1505.4.4 lists 100 cfm intermittent or 25 cfm continuous for kitchens. ASHRAE 62.2-2013 Addendum c also sets 100 cfm for a vented range hood, and for continuous exhaust it asks for 5 air changes per hour of kitchen volume, in enclosed kitchens only.- Kitchen fan that is not a hood
300 CFM, or in an enclosed kitchen a capacity of 5 ACH = volume x 5 / 60ASHRAE 62.2-2013 Addendum c, Table 5.1, covers ceiling and wall fans and downdraft units. Shown for reference, since a hood over the range captures cooking fumes at a much lower airflow.- Makeup air check
recommended CFM > 400 and a fuel-burning appliance inside the air barrier2021 IRC M1503.6 requires makeup air approximately equal to the exhaust rate for an exhaust system capable of more than 400 cfm when a fuel-burning appliance that is neither direct-vent nor mechanical draft sits inside the air barrier. BuildSolver reads a gas range as such an appliance, so answer yes for one. That is our interpretation of M1503.6, and your code official may read it differently.
Worked examples across four ranges
All four sit in the same 14 x 12 ft open kitchen with a 9 ft ceiling. What changes is the range width, the hood location and the fuel, and only the gas range counts as a fuel-burning appliance, so it is the one row where the makeup air check can come into play. Treat the gas rule column as a reference. It never sets the recommended airflow.
| Range | HVI rate | Gas rule, reference | Recommended | Makeup air |
|---|---|---|---|---|
| 30 in electric range, against a wall | 250 CFM | N/A | 250 CFM | Not triggered |
| 36 in gas range, 40,000 BTU/h, against a wall | 300 CFM | 400 CFM | 300 CFM | Not triggered |
| 36 in electric cooktop, over an island | 450 CFM | N/A | 450 CFM | Not triggered |
| 48 in electric range, against a wall | 400 CFM | N/A | 400 CFM | Not triggered |
The 36 in gas range sizes at 300 CFM on the HVI rate. HVI sets it. A gas rule of thumb would say 400 CFM, but with no code or HVI source behind it, that number stays for reference only. At 300 CFM the hood is at or under the 400 CFM line, so makeup air is not triggered even with a gas range in the house. Pick a model capable of more than 400 CFM and that answer changes. The island cooktop needs 450 CFM, 150 CFM more than the same cooktop against a wall. That puts it over 400 CFM, but with no fuel-burning appliance in this house the makeup air condition is not met.
Standards and data sources
- Home Ventilating Institute (HVI), How Much Ventilation Do I Need? - recommended rates of 100 CFM per linear foot of range against a wall and 150 over an island, and minimums of 40 and 50.
- HVI range hood brochure - the same per-foot table with worked hood widths (250, 300 and 400 CFM for 30, 36 and 48 in against a wall) and the guidance that hood width should match the range.
- International Residential Code (IRC) 2021, Table M1505.4.4 - the kitchen local exhaust minimum of 100 cfm intermittent or 25 cfm continuous.
- International Residential Code (IRC) 2021, Section M1503.6 - makeup air for an exhaust system capable of more than 400 cfm where a fuel-burning appliance that is neither direct-vent nor mechanical draft is inside the air barrier.
- ANSI/ASHRAE Standard 62.2-2013, Addendum c, Tables 5.1 and 5.2 - 100 cfm for a vented range hood, 300 cfm or 5 ACH for other kitchen fans, 5 ACH continuous in an enclosed kitchen, and the 60 sq ft enclosed kitchen definition.
Limitations of this calculator
- The CFM here is the airflow the hood should deliver. Ducts cut into that. Duct size, length, elbows and the roof or wall cap all lower real airflow, so check the hood's rating at the static pressure your duct run adds.
- Capture efficiency depends on hood depth, overhang and mounting height as much as on CFM. This calculator does not model capture velocity.
- The gas rule of 100 BTU/h per CFM is a common field rule, not an HVI, IRC or ASHRAE requirement. It shows as a reference row and does not change the recommended airflow or the makeup air check.
- The makeup air row reads IRC M1503.6 as written in the 2021 IRC, and the appliance condition comes only from your answer. BuildSolver reads a gas range as qualifying, which is an interpretation of the section. Some jurisdictions amend the section, and some adopt their own kitchen hood airflow tables, so check the locally adopted code.
- The 2024 IRC keeps the same 400 cfm trigger in M1503.6 but asks for not fewer than one outdoor air duct and damper, where the 2021 text asks for one damper. Check the edition your jurisdiction adopted.
- M1503.6 keys on what the installed hood can exhaust. A hood rated above 400 CFM triggers it even when this page recommends less, so compare the model you pick against the threshold too.
- Commercial kitchens (NFPA 96, IMC Section 507), downdraft units and outdoor kitchens are outside this calculator.
- Preliminary sizing for the sales-phase conversation. The hood model, sone rating and duct layout are separate steps.
Common range hood sizing mistakes
- Using the wall rate for an island hood. An island hood has no wall behind it to steer the plume, which is why HVI raises the rate from 100 to 150 CFM per linear foot. A 36 in island cooktop needs 450 CFM on the HVI rate, not 300.
- Buying the biggest hood in the showroom. A hood capable of more than 400 CFM can pull you into makeup air under 2021 IRC M1503.6 when there's a gas range or an atmospheric appliance inside the air barrier. Size to the job. Then pick the hood.
- Treating the BTU rule as code. One CFM per 100 BTU/h gets repeated a lot for pro-style gas ranges, but no HVI, IRC or ASHRAE text gives it. That's why this page shows it for reference and sizes the hood on the HVI rate and the code minimum.
- Recirculating hoods counted as exhaust. A ductless hood filters grease and returns the air to the kitchen. ASHRAE 62.2-2013 Addendum c sets its 100 cfm figure for a vented range hood, and the IRC table covers exhaust to the outdoors, so a recirculating unit does not meet either one.
- Ignoring the duct. A hood rated at a free-air number drops fast behind a long run with several elbows or a duct smaller than the hood collar. Match the collar. Keep the run short and straight.
Common questions about range hood CFM
How many CFM does a 30 inch range hood need?
Against a wall, HVI recommends 100 CFM per linear foot of range, so a 30 inch range needs 250 CFM. HVI's minimum for the same range is 100 CFM. Over an island the recommended rate rises to 375 CFM, because an island hood has no wall behind it to steer the rising plume into the canopy.
How many CFM does a 36 inch range hood need?
300 CFM against a wall and 450 CFM over an island on the HVI recommended rate. Both are above the 100 CFM code minimum, so the HVI rate sets the number.
What is the code minimum for a kitchen range hood?
2021 IRC Table M1505.4.4 lists 100 cfm intermittent or 25 cfm continuous for kitchens, and ASHRAE 62.2-2013 Addendum c sets 100 cfm for a vented range hood. Your jurisdiction may have amended those numbers.
When does a range hood need makeup air?
Under M1503.6 in the 2021 IRC, when the exhaust system can move more than 400 cfm and a fuel-burning appliance that is neither direct-vent nor mechanical draft is inside the air barrier. Makeup air then has to be approximately equal to the exhaust rate, with at least one damper. The 2024 IRC asks for an outdoor air duct and damper. An all-electric house with direct-vent equipment does not meet the appliance condition.
Does a gas range need a bigger hood than an electric range?
No. HVI's per-foot rate is the same for both, and so is the code minimum. You'll hear a rule of 1 CFM per 100 BTU/h of burner input, but no HVI, IRC or ASHRAE text states it, so this calculator shows it for reference only. Where a gas range does matter is makeup air, since it counts as a fuel-burning appliance under 2021 IRC M1503.6.
Can a kitchen use a ceiling exhaust fan instead of a hood?
ASHRAE 62.2-2013 Addendum c allows other kitchen exhaust fans, including downdraft units, at 300 cfm. In an enclosed kitchen such a fan can also meet a capacity of 5 kitchen air changes per hour, and the table note for enclosed kitchens requires a vented range hood when the fan's rate is below 5 kitchen air changes per hour.
What is an enclosed kitchen in ASHRAE 62.2?
In ASHRAE 62.2-2013 Addendum c, a kitchen whose permanent openings to adjacent interior spaces total 60 sq ft or less. An open kitchen must use demand-controlled exhaust. Continuous exhaust at 5 ACH is only an option in an enclosed kitchen.
Used on the same job
Run the whole-house load in chat
The chat has no range hood or kitchen exhaust tool, so the hood airflow comes from this page. Describe the house in chat and the assistant runs the free whole-house Manual J cooling and heating load for the same job.
Open the chat