How We Rank Air Purifiers

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.

The ratings and their weights

Rating	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.
Energy 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.
Quietness	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.
Certified CADR	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.
Tested performance	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.

Why rankings are shown within room-size classes

Cross-class comparisons are rarely what a buyer needs, so every page ranks within one of these:

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.
We don't copy reviewers' text. We record their numbers and link to their work.

How the site makes money

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. More in About.

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