Range hood CFM calculator: how many CFM does my range hood need?
250 cfm range hood
100 cfm per ft on a wall (HVI); 100 cfm at the least · for a 30 in range
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Enter it the way you measured it: 4.5, 4 1/2,
3/8 or 10' 6".
250 cfm range hood
100 cfm per ft on a wall (HVI); 100 cfm at the least
Source: International Residential Code 2021, Sections M1503.6 and Table M1505.4.4, and HVI range hood rates, read October 27, 2026. Read the source
A 30 in range against a wall needs a 250 cfm range hood at HVI's 100 cfm per linear foot, and no less than 100 cfm, HVI's minimum and the IRC 2021 kitchen floor; over an island, 150 cfm per foot.
A worked example
A 42 in cooktop in an island, in a house with an atmospheric gas water heater in the basement needs a 525 cfm range hood. 42 in is 3.5 ft, and over an island HVI recommends 150 cfm per foot: 525 cfm, with 175 at the least. Above 400 cfm with a natural-draft water heater inside, IRC M1503.6 asks for makeup air at about the same rate.
How many CFM for a 30 or 36 inch range hood?
Against a wall HVI recommends 250 cfm for 30 in and 300 for 36 in, with 100 and 120 at the least. Over an island multiply by 1.5: 375 and 450 cfm.
When does a range hood need makeup air?
Above 400 cfm, if the house has a fuel-burning appliance inside that is neither direct-vent nor power-vented, such as an atmospheric water heater: IRC M1503.6 asks for makeup air at about the hood rate. A hood of 400 cfm or less is outside the rule.
What is the code minimum for a kitchen hood?
100 cfm intermittent or 25 cfm continuous, by IRC 2021 Table M1505.4.4. HVI's own minimum, 40 cfm per foot on a wall, reaches it at a 30 in range.
What else it is called
Also searched as a kitchen hood CFM calculator, range hood size calculator or vent hood CFM calculator. CFM is cubic feet per minute, the airflow on the hood label and in the HVI-Certified Products Directory.
Hood cfm by range width
| Range width | Wall, recommended | Wall, at the least | Island, recommended | Island, at the least |
|---|---|---|---|---|
| 24 in | 200 cfm | 100 cfm | 300 cfm | 100 cfm |
| 30 in | 250 cfm | 100 cfm | 375 cfm | 125 cfm |
| 36 in | 300 cfm | 120 cfm | 450 cfm | 150 cfm |
| 42 in | 350 cfm | 140 cfm | 525 cfm | 175 cfm |
| 48 in | 400 cfm | 160 cfm | 600 cfm | 200 cfm |
| 60 in | 500 cfm | 200 cfm | 750 cfm | 250 cfm |
HVI: 100 cfm recommended and 40 at the least per linear foot of range against a wall, 150 and 50 over an island; never under the 100 cfm intermittent of IRC 2021 Table M1505.4.4. Above 400 cfm, a house with a natural-draft fuel-burning appliance inside needs makeup air (IRC M1503.6).
Where the numbers come from
- Rate: Home Ventilating Institute, How Much Ventilation Do I Need?, kitchen range hoods. Per linear foot of range, against a wall 100 cfm recommended and 40 at the least, in an island 150 and 50; a 30 in hood 250 and 100, 36 in 300 and 120, 48 in 400 and 160; over islands multiply by 1.5. Read October 27, 2026. HVI ventilation guidelines
- Code: International Residential Code 2021, as adopted by Colorado without amendments. Table M1505.4.4: kitchens 100 cfm intermittent or 25 cfm continuous. M1503.6: where a fuel-burning appliance that is neither direct-vent nor mechanical-draft is inside the dwelling air barrier, an exhaust system over 400 cfm needs makeup air at about the exhaust rate. Read October 27, 2026. IRC 2021 chapter 15 on UpCodes
- The rest is arithmetic: cfm = range width in ÷ 12 × the rate per foot, rounded up.
The rates are for a canopy hood over the range. Downdraft exhausters and professional-style cooktops go by the range or cooktop maker, as HVI says. A recirculating hood moves no air outdoors.
By Javier Miralles · Last updated . How this site is made.
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