Room Air Change Check Calculator
Check a room's air changes per hour from CFM.
Enter your values
ⓘ Live results
Results
- Room volume
- 1,200 cu ft
- Air changes per hour
- 6
- Assessment
- Typical residential range
Quick answer
Air changes per hour equals the room's supply CFM multiplied by 60 and divided by the room volume.
ACH = CFM x 60 / room volume
How to use the Room Air Change Check Calculator
- 1Enter the room's supply CFM from the duct design.
- 2Enter the room's floor area and ceiling height for volume.
- 3Compare the resulting ACH to the 4-8 range typical of well-designed residential rooms.
Worked example
Using the values the calculator loads with:
Inputs
- Supply CFM120 CFM
- Room area150 sq ft
- Ceiling height8 ft
Results
- Room volume1,200 cu ft
- Air changes per hour6
- AssessmentTypical residential range
Frequently asked questions
What ACH should a bedroom have?
Around 4-6 air changes per hour is comfortable for most bedrooms.
Why check this after sizing CFM by area?
It's a sanity check — a room with unusual ceiling height can end up under- or over-ventilated even if CFM per square foot looks right.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.