Range Hood CFM Calculator

Use the industry rule of thumb: 1 CFM per 100 BTU of total burner output. A gas cooktop with 55,000 BTU across all burners needs 55,000 divided by 100 = 550 CFM. Because 550 CFM is over the 400 CFM threshold in IRC M1503.6, this hood also requires dedicated makeup air at roughly the same rate — check your local amendments, since some jurisdictions add exceptions.

For electric or induction cooktops, use the HVI width method: a wall-mounted hood needs 100 CFM per linear foot of cooktop (recommended) or 40 CFM per foot (minimum). A 30 inch cooktop is 2.5 feet, so the HVI recommended size is 2.5 times 100 = 250 CFM, with a minimum of 2.5 times 40 = 100 CFM. These figures come straight from the 2008 HVI range hood brochure, which lists 250 CFM recommended and 100 CFM minimum for a 30 inch wall hood.

Use both and take the larger — that is what Mode 3 of this calculator does. Example: a 36 inch gas range with four 15,000 BTU burners gives 60,000 BTU total, so the BTU method says 60,000 divided by 100 = 600 CFM. The width method says 3 feet times 100 CFM per foot = 300 CFM. The winner is 600 CFM. At 600 CFM you are over the 400 CFM IRC M1503.6 threshold, so plan for makeup air as well.

Multiply kitchen length by width by ceiling height, then divide by 4 — that equals 15 air changes per hour. A 12 ft by 12 ft kitchen with an 8 ft ceiling is 1,152 cubic feet, so 1,152 divided by 4 = 288 CFM. Check: 1,152 times 15 divided by 60 = 288 CFM. Treat this as a sanity check rather than the primary sizer; compare it with the BTU or width method and use the larger number.

Follow the Proline rule of thumb: add 1 CFM for every foot of duct, 25 CFM for every elbow or turn, and 40 CFM if the duct ends in a roof cap. Example: 12 feet of duct plus 2 elbows plus a roof cap adds 12 plus 50 plus 40 = 102 CFM. So if your cooktop needs 600 CFM, shop for a hood rated at least 702 CFM — in practice that means a 750 CFM class unit. Short, smooth, rigid duct always beats adding CFM.

Multiply CFM by 1.699. A 600 CFM range hood moves 600 times 1.699 = 1,019.4 cubic meters per hour. European and Asian hood listings often quote m3/h instead of CFM, so this conversion lets you compare a 550 CFM US hood (about 934.5 m3/h) against a 1,000 m3/h import on equal footing.

IRC M1503.6 (2018) requires any exhaust system capable of exhausting more than 400 CFM to be provided with makeup air at a rate approximately equal to the exhaust rate, typically through a gravity or motorized damper that opens with the hood. Without it, a powerful hood depressurizes a tight house and can backdraft a furnace, water heater, or fireplace, spilling carbon monoxide indoors. The 2009 and 2015 IRC put the same rule at M1503.4, and some states add exceptions — always check local amendments.

No — this tool sizes kitchen range hoods, which capture grease, smoke, and combustion byproducts with completely different formulas and code sections than other equipment. For bathroom humidity, use our bathroom fan CFM calculator. Evaporative (swamp) coolers are supply-side cooling, not exhaust, so they need their own sizer. Furnace, water heater, boiler, air conditioner, generator, and septic tank sizing each follow their own standards and are not covered here.

Sones measure perceived loudness: 1 to 2 sones is about as quiet as a refrigerator (HVI defines 1 sone as a 1,000 Hz tone at 40 dB), 3 to 4 sones is roughly normal conversation level, and 8 sones or more is vacuum-cleaner loud. A practical trick: buy more CFM than you need and run the hood on a lower speed for quieter daily cooking. Mounting height is typically 24 to 30 inches above electric cooktops and 30 to 36 inches above gas — always follow your specific hood manufacturer's installation instructions.