CompareSmartDeviceSmart Air Purifiers

What size air purifier for my room?

Enter your room. We compute air changes per hour (ACH) from AHAM CADR figures — math shown. A purifier qualifies only if it reaches 4.8 ACH in your room at your ceiling height; manufacturer coverage claims are never taken on faith.

Main concern

Not sure what matters? Answer 4 questions instead with the Purifier Finder quiz, or browse the full comparison hub.

The math, in full

V_ft³ = area_m² × 10.7639 × height_m × 3.28084 # or area/height entered in ft directly CADR_req = 4.8 × V_ft³ ÷ 60 # cfm needed for 4.8 air changes/hour ACH = CADR_eff × 60 ÷ V_ft³ # achieved by a model qualify ⇔ ACH ≥ 4.8 using the concern-channel CADR display convention: ~area_eq_ft² = CADR_eff × 1.55 # labeled industry shorthand, NOT used for qualification

Qualification always uses the exact formula above. The ×1.55 figure is an industry display shorthand (manufacturers round 60 ÷ (4.8 × 8) = 1.5625 down to ~1.55), so expect occasional small differences (~0.8%) vs manufacturer-published room sizes — those never decide a match here. Units: 1 m = 3.28084 ft, 1 m² = 10.7639 ft². Default ceiling 2.44 m = 8 ft, adjustable 2.20–4.00 m — never a hidden assumption.

Where a manufacturer publishes one combined CADR without naming the test aerosol, that number is used and labeled as a combined rating. For pet dander there is no AHAM test aerosol: dust CADR is used as closest proxy and every card says so. Models with no published CADR and no manufacturer room-size rating are listed under “Cannot verify fit” rather than guessed. Ozone statuses are checked against the California CARB certified-device list; models without a verified entry are excluded from recommended slots.

Independent comparison. Prices are point-in-time scrapes from Amazon.com listings, not offers. CADR figures render only where two independent sources agree; ozone status is checked against the California Air Resources Board certified-device list. No health claims beyond manufacturer documentation.