CFM Calculator
Find the airflow (CFM) a room needs from its volume and the air changes per hour you want.
Change the values and press Calculate to work out your own figures.
From the room's size
Enter the room's size and the air changes per hour.
Show the working
- CFM = volume × air changes per hour ÷ 60
From the volume
Enter the volume and the air changes per hour.
Show the working
- CFM = volume × air changes per hour ÷ 60
How to use it
Enter the room's size and the air changes per hour. Enter the volume and the air changes per hour.
Lengths can be decimals, fractions or tape entries such as 12' 6 1/2" (in feet or inches). Prices are optional.
Key facts
CFM = volume (cu ft) × air changes per hour ÷ 60
Rates
Living rooms 3–4 air changes an hour, bedrooms 5–6, kitchens and bathrooms 7–8, laundries 8–9.
Questions
What CFM fan for a 10 × 10 × 8 ft room at 8 ACH?
106.67 CFM.
Formulas
CFM = volume (cu ft) × air changes per hour ÷ 60
Sources
Limitations
- Material densities are typical values (the midpoint of the commonly published range); real loads vary with moisture, grading and compaction, so check with your supplier or type in their density.
- Tank results are the geometric volume; real tanks have wall thickness and fittings.