Free Tools
Range hood CFM calculator.
Size the ventilation for your kitchen. Calculate by cooktop power or by room size, factor in your cooking and ductwork, and get the minimum CFM your range hood should pull.
Add up the BTUs of every burner — 100 CFM per 10,000 BTU.
Ductwork (optional)
+1 CFM / ft
+25 CFM each
Recommended minimum
This is a minimum, not a ceiling. You can't raise a hood's CFM after you buy it, and most kitchens do best with at least 600 CFM — so when you're between sizes, scale up. Island hoods (exposed on all sides) need more than wall-mounted ones, where the back wall helps funnel air. Match your duct size to the airflow: too small, too long, or too many bends and even a powerful blower can't clear the air.
Rated CFM is a lab number. Installed CFM is what you actually get.
The CFM printed on the box is a lab rating — HVI‑certified hoods are tested on a standardized rig at a fixed static pressure (commonly 0.1 in. w.g.), not in a real kitchen. Your install adds resistance the lab never saw: duct size and length, every elbow, the roof or wall cap, make‑up air, and dirty filters all drag the real number down. A hood rated 600 CFM can move far less through a long, undersized, twisty duct run.
And airflow isn't the whole story — ASHRAE notes that CFM ratings say nothing about capture efficiency: how well the hood actually grabs smoke, grease, and steam over the cooktop. A big number on a bad install still leaves the kitchen hazy.
Why a strong‑sounding blower can still pull weak
If the hood is loud but the air barely moves, the blower is usually fine — the installation is the bottleneck. Check duct size, elbows, the damper, the cap, the filters, and make‑up air before blaming the unit.