What CFM means
CFM means cubic feet per minute, the volume of air a fan, register or duct moves. It is the basic unit of airflow in heating, cooling and ventilation.
Also called cubic feet per minute, airflow.
Where it matters on a HVAC job
Low airflow causes frozen coils, high bills and rooms that never get comfortable. Duct sizing, register sizing and exhaust fans are all chosen by CFM. Measuring it, rather than guessing from the unit's tonnage, is what separates a real diagnosis from a parts swap.
What the model code says
- A kitchen or other exhaust that can pull more than 400 cubic feet per minute needs makeup air when the home has certain fuel-burning appliances. (IRC 2021, Chapter 15)
Check which code edition your building department enforces for CFM before you quote.
What it costs
For CFM, the closest koira.ai price is the ductwork replacement cost guide, near $1,250 for a typical job and $450 to $2,200 for most. The guide shows its sources and what moves the price. The cfm calculator prices a job line by line.
Work it out
- Free calculator: CFM calculator
- Cost guide: Ductwork replacement cost
- Licensing: HVAC license rules by state
- Tools, templates and guides: Free HVAC resources
Sources: 2021 International Residential Code, Chapter 15, Exhaust Systems (ICC). Checked October 9, 2026.