Range hood buying guide: size, CFM and ducting

A range hood is the appliance people most often under-buy, and the one they notice every time they sear a steak. Size and ducting matter more than the look.

How wide

The hood should be at least as wide as the cooktop, and ideally 3" wider on each side (a 36" hood over a 30" range). Island hoods should be wider still, because air moves in from every side.

How much CFM

• Electric or induction: about 10 CFM per inch of cooktop width is plenty for most cooking.
• Gas: about 1 CFM per 100 BTU of total burner output (a 60,000 BTU range wants about 600 CFM).
• The range hood CFM calculator does it for your range.

Ducted or ductless?

Ducted hoods vent to the outside and actually remove heat, smoke and moisture. Ductless (recirculating) hoods filter grease and odor and blow the air back into the kitchen; use them only when ducting is impossible. Keep duct runs short and straight, with as few elbows as possible.

Mounting height

Most hoods mount 24" to 30" above an electric cooktop and 27" to 36" above gas; always check the manufacturer's range, since too high loses capture and too low blocks your view of the back burners.

Make-up air

Many codes require make-up air for hoods over about 400 CFM, so the fan does not pull air (or combustion gases) back down a chimney. Plan it with the hood, not after. We size this as part of a kitchen remodel.

Noise

Noise is rated in sones: under 1.5 is quiet, 4 is conversation level, 7 or more is loud. Remote (in-line or exterior) blowers move the noise out of the kitchen on powerful hoods.

Common questions

How many CFM do I need for a gas range?

About 1 CFM per 100 BTU of total burner output: roughly 600 CFM for a 60,000 BTU range.

How high should a range hood be above the stove?

Usually 24" to 30" above electric cooktops and 27" to 36" above gas. Follow the manufacturer's range.

Is a ductless range hood worth it?

Only when venting outside is not possible. It filters grease and odor but does not remove heat or moisture.