Air Purifier Size Calculator
Enter your room dimensions to find the minimum CADR your air purifier needs to hit — then see real purifiers from our catalog that meet or beat that number.
Your room
Air changes per hour
Minimum CADR
For a 300 sqft room with 8' ceilings (2,400 ft³)
Smoke CADR (the one that matters most)
200CFM
Dust
220 CFM
Pollen
200 CFM
Why smoke CADR? It's the toughest particle size to filter, so any purifier hitting this number will clean your room of dust and pollen too. Look for AHAM Verifide certification when shopping.
Purifiers that hit 200 CFM smoke CADR
Sorted by closest match to your needs, then by price. Real specs from our catalog.
Winix
WINIX 5520 Air Purifier for Home Large Room Up to 1882 Ft² in 1 Hr With Air Quality Monitor, True HEPA, High Deodorization Carbon Filter and Auto Mode, Captures Pet Allergies, Smoke, Dust.
LEVOIT
LEVOIT Air Purifiers for Home Large Room Up to 1733 Ft² With HEPA Sleep Mode, AHAM VERIFIDE, Auto Mode, Air Quality Monitor, Smart WiFi, 3-in-1 Filter For Pet Allergy, Smoke, Dust, Core 400S-P, White
LEVOIT
LEVOIT Air Purifiers for Home Large Room Up to 1875 Ft² with Washable Pre-Filter, AHAM VERIFIDE, Air Quality Monitor, HEPA Sleep Mode for Allergies, Pet Hair in Bedroom, Vital 200S-P, White
Coway
Coway Airmega AP-1512HH(W) True HEPA Purifier with Air Quality Monitoring, Auto, Timer, Filter Indicator, and Eco Mode, 16.8 x 18.3 x 9.7, White AP-1512HH WHITE
How this calculator works
What is CADR and why does it matter?
Clean Air Delivery Rate measures cubic feet of filtered air a purifier delivers per minute, certified by AHAM. Higher CADR = bigger rooms cleaned faster. Look for the AHAM Verifide seal — manufacturer-claimed numbers without it are often inflated.
How is the minimum CADR for my room calculated?
Room volume (sqft × ceiling height) × air changes per hour ÷ 60 = required CFM. For most homes 4-5 ACH is plenty; allergies or smoke push you to 6 ACH; clinical settings hit 8 ACH.
Why focus on the smoke CADR number?
Smoke particles are the smallest of the three CADR test particles, so any purifier that hits your target smoke CADR will easily handle dust and pollen too. Smoke is the worst-case design point.
Should I oversize the purifier?
A bit, yes. Running an oversized purifier on its lowest, quietest setting filters as well as a smaller unit running flat-out — and uses less energy and noise. Aim for ~125% of your calculated CADR if you can.