What is CADR?
CADR (Clean Air Delivery Rate) measures how quickly an air purifier can filter smoke, dust, and pollen from the air. A higher CADR means faster air cleaning. Use this calculator to find the minimum CADR needed for your room.
Enter Your Room Size
sq ft
Recommended CADR
Minimum CADR
0 CFM
Recommended CADR
0 CFM
How CADR is Calculated
The standard recommendation is that CADR should be at least 2/3 of your room's square footage. For example, a 300 sq ft room needs at least 200 CFM CADR.
Minimum CADR = Room Area (sq ft) x 2/3
- 1 Measure your room's length and width in feet
- 2 Calculate the area (length x width)
- 3 Multiply by 2/3 to get minimum CADR
- 4 Add 20-30% buffer for recommended CADR
CADR Tips
Higher CADR = faster air cleaning, but also usually more noise
Consider slightly oversizing for rooms with high ceilings
Smoke CADR is typically lowest, use it as your benchmark
Running on lower speeds reduces effective CADR
CADR FAQ
What's the difference between Smoke, Dust, and Pollen CADR?
Air purifiers are rated for three particle sizes: Smoke (0.09-1.0 microns), Dust (0.5-3.0 microns), and Pollen (5.0-11.0 microns). Smoke CADR is typically the lowest and most important rating.
Is higher CADR always better?
Higher CADR cleans air faster, but also usually means more noise and energy use. Match CADR to your room size - oversizing too much wastes money.
What if my room has high ceilings?
For ceilings over 8 feet, increase the recommended CADR by 20-25% to account for additional air volume.