How to Use the Air Purifier CADR Calculator
The key performance number for an air purifier is its CADR (Clean Air Delivery Rate), which measures how much filtered air it delivers per minute, tested and certified by AHAM (the Association of Home Appliance Manufacturers). AHAM's widely-cited sizing guideline says a purifier should have a CADR of at least two-thirds of your room's square footage for adequate performance, and a CADR equal to the full square footage for optimal results.
Enter your room's area in square feet and this calculator instantly shows both the minimum acceptable CADR and the optimal CADR to look for. Since most purifiers run quieter — and therefore less effectively — below their maximum fan speed, choosing a unit rated at or above the optimal CADR gives you room to run it on a lower, quieter setting while still keeping the air clean.
Frequently Asked Questions
CADR (Clean Air Delivery Rate) measures how much filtered air a purifier delivers per minute, tested and certified by AHAM. A higher CADR means faster air cleaning.
AHAM recommends a CADR of at least two-thirds of your room's square footage for adequate performance, and a CADR equal to your room's square footage for optimal results.