Air Purifier CADR to ACH Calculator
Air changes per hour from a purifier's CADR rating.
Enter your values
ⓘ Live results
Results
- Air changes per hour
- 11.25
- Room volume
- 1,600 cu ft
- Assessment
- Good for general air cleaning (5+ ACH)
Quick answer
Air changes per hour equal the purifier's CADR in CFM multiplied by 60 and divided by the room volume.
ACH = CADR x 60 / room volume
How to use the Air Purifier CADR to ACH Calculator
- 1Find the purifier's CADR rating (usually for smoke, dust or pollen in CFM).
- 2Compute the room volume from area and ceiling height.
- 3Multiply CADR by 60 and divide by volume to get ACH.
Worked example
Using the values the calculator loads with:
Inputs
- CADR rating300 CFM
- Room area200 sq ft
- Ceiling height8 ft
Results
- Air changes per hour11.25
- Room volume1,600 cu ft
- AssessmentGood for general air cleaning (5+ ACH)
Frequently asked questions
What ACH is considered good?
4-6 ACH is a common target for general indoor air quality improvement; 5-8 for infection control support.
CADR vs HEPA ACH claims?
CADR already accounts for filter efficiency and fan speed, making it the most realistic comparison metric.
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.