How to Use the Kitchen Hood CFM Calculator
Shopping for a range hood, the CFM number on the spec sheet doesn't tell you much on its own — you need to know how much airflow your specific kitchen actually needs. This calculator estimates that based on your kitchen's size and how intensely you cook, using how many times per hour the air in the kitchen should be fully exchanged.
It multiplies your kitchen's volume (area times a fixed 8-foot ceiling height) by an air-changes-per-hour (ACH) rate, then converts that to CFM (cubic feet per minute). Everyday home cooking uses an ACH of about 15, while high-heat cooking like wok cooking or heavy frying uses a higher ACH of about 20, since it generates more heat, smoke, and grease-laden vapor. A bigger kitchen or a higher-intensity cooking style means a higher CFM requirement.
Keep in mind that real-world performance is affected by duct length, the number of elbows, and filter condition, all of which reduce actual airflow below a hood's rated maximum. Treat this calculation as a minimum baseline and choose a model rated somewhat above it for reliable performance.
Frequently Asked Questions
Real installations lose airflow to duct length, elbows, and filter resistance, so actual performance is usually lower than a hood's rated maximum CFM. Choosing a model rated above your calculated need gives you margin for a quieter, more effective setup.
Yes — high-heat cooking produces more heat, smoke, and grease-laden vapor in a short time, so it needs a higher air-change rate. This calculator applies a higher ACH automatically when you select high-heat cooking.