How we rank air purifiers
Every air purifier gets a score from 0 to 100, shown as 1.0–5.0 stars. The score is a weighted sum of the components below. Value and noise are normalized within each room-size class, because bigger units cost more and run louder; efficiency, filter cost and features are normalized across the whole catalog, with the top and bottom 5% clipped so one outlier cannot distort the scale. Nothing is hand-adjusted, and manufacturers have no input.
The components
| Component | Weight | What it measures | Why it matters |
|---|---|---|---|
| Value | 25% | Smoke CADR (cfm) per dollar at current street price, compared within the room-size class | CADR is the one number that tells you how much clean air a unit delivers. Price per CADR is the fairest value measure. |
| Efficiency | 10% | Smoke CADR per watt at maximum fan speed | A unit that runs all day costs real money; CADR per watt separates good motors and filters from brute force. |
| Noise | 15% | Rated sound level at maximum speed, lower is better, compared within class | Most people never use the top speed because it is too loud. A quieter top speed means more usable CADR. |
| Filter_cost | 15% | Annual replacement-filter cost per 100 CADR, lower is better | Over five years filters often cost more than the unit. We show five-year cost of ownership on every page. |
| Certification | 10% | AHAM Verifide listing scores 1.0; manufacturer-claimed CADR scores 0.3 | AHAM certifies CADR through independent lab testing. Uncertified CADR claims are routinely optimistic. |
| Features | 10% | Points for auto mode with a particle sensor (1), true HEPA (1), washable prefilter (1), at least 1 lb of activated carbon (1), app (0.5), Energy Star (0.5) | Small weight on purpose. A particle sensor and a real carbon bed change what the unit can do; the rest is convenience. |
| Measured | 15% | Independently measured CADR as a percent of the rated figure, or lab clean-time results converted to the same scale | When a lab has tested the unit, that beats the spec sheet. Dropped when no measurement exists, with the other weights rescaled. |
Room-size classes
Rankings are shown within room-size classes, because cross-class comparisons are rarely what a buyer needs:
- Compact (under 130 CADR) — Bedrooms and offices up to about 200 sq ft.
- Medium (130–249 CADR) — Large bedrooms and living rooms up to about 380 sq ft.
- Large (250–399 CADR) — Open living areas up to about 600 sq ft.
- Extra Large (400+ CADR) — Great rooms, basements and open floor plans.
Where the data comes from
CADR figures come from AHAM Verifide listings where the unit is certified and from manufacturer spec sheets otherwise; the page says which. Filter prices are the manufacturer's current replacement price. Prices are approximate street prices and are refreshed periodically. Measurements come from the reviewers and labs we track; we store the number, unit, source and link, and never copy a reviewer's text. See the reviewers and labs we track.
What we don't do
- We don't accept payment, sponsorship or free products for placement.
- We don't adjust scores by hand. If a ranking looks wrong, the fix is a data correction or a formula change, and formula changes are noted on the updates page.
- We don't rank air purifiers we can't find a spec sheet and a current price for.
Affiliate disclosure
Links to retailers are affiliate links and may earn us a commission at no cost to you. We link to every ranked air purifier the same way, so there is no incentive to favor one over another.