Air purifiers, by the room they really clean
The box says 2,207 sq ft205 m². It really cleans 431 sq ft40 m².
The boxes on our list only work if the air in the room is changed 0.8 to 4.7 times an hour. We size every purifier at 4.8, AHAM's reference, so the room size you see here is the one it can really keep clean.
How big is your room?
- 107 sq ft10 m² 10 m²107 sq ft
- 161 sq ft15 m² 15 m²161 sq ft
- 215 sq ft20 m² 20 m²215 sq ft
- 269 sq ft25 m² 25 m²269 sq ft
- 322 sq ft30 m² 30 m²322 sq ft
- 376 sq ft35 m² 35 m²376 sq ft
- 430 sq ft40 m² 40 m²430 sq ft
- 538 sq ft50 m² 50 m²538 sq ft
- 645 sq ft60 m² 60 m²645 sq ft
- 861 sq ft80 m² 80 m²861 sq ft
- 1,076 sq ft100 m² 100 m²1,076 sq ft
Pick the size at or just above yours. Exact size or a high ceiling? Use the calculator
Drawn to scale: the box says “Quickly cleans 439 ft² every 12.5 minutes & 2,207 ft² in 1 hour”, the purifier really cleans 431 sq ft, 5.1 times less.Drawn to scale: the box says “Quickly cleans 439 ft² every 12.5 minutes & 2,207 ft² in 1 hour”, the purifier really cleans 40 m², 5.1 times less.
Blueair Blue Pure 311i Max, drawn to scale. Box: “Quickly cleans 439 ft² every 12.5 minutes & 2,207 ft² in 1 hour”. Smoke CADR at 4.8 air changes: 431 sq ft40 m².
4.5× how much the average box on our list overstates real coverage
26 purifiers listed, 17 with an AHAM-certified CADR, every figure sourced and dated
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The short list
Our pick for every room size
Every pick reaches 4.8 air changes an hour in that room on a verified CADR. Tap a size for the alternatives, trade-offs and the Amazon link.
| Room | Our pick | Options |
|---|---|---|
| 107 sq ft10 m² 10 m²107 sq ft | GermGuardian AC4825E | 16 models |
| 161 sq ft15 m² 15 m²161 sq ft | Levoit Core 300 | 14 models |
| 215 sq ft20 m² 20 m²215 sq ft | Levoit Core 400S-P | 14 models |
| 269 sq ft25 m² 25 m²269 sq ft | Levoit Core 400S-P | 11 models |
| 322 sq ft30 m² 30 m²322 sq ft | Winix T810 | 11 models |
| 376 sq ft35 m² 35 m²376 sq ft | Winix 9800 | 10 models |
| 430 sq ft40 m² 40 m²430 sq ft | Levoit EverestAir-P | 7 models |
| 538 sq ft50 m² 50 m²538 sq ft | Medify MA-112 | 4 models |
| 645 sq ft60 m² 60 m²645 sq ft | Medify MA-112 | 2 models |
| 861 sq ft80 m² 80 m²861 sq ft | Medify MA-112 | 1 model |
| 1,076 sq ft100 m² 100 m²1,076 sq ft | 2 × Levoit EverestAir-P | 2 units |
Method
How we pick, in three steps
- 1
Start from verified smoke CADR
The clean air delivery rate for smoke, the smallest particles, from AHAM's independent directory wherever it exists. Not the marketing number.
- 2
Divide by 4.8 air changes
CADR (m³/h) ÷ (4.8 × 2.5 m) = room it really cleans
4.8 is the rate AHAM's own room-size guideline is built on: enough to cut smoke particles by about 80%.
- 3
Pick for the room, not the box
We choose verified models with air to spare for your room, so they needn't run flat out.
Who's behind this
BuyBySpecs Team
We don’t test purifiers ourselves. We gather each model’s figures from sources you can check, AHAM’s certified CADR directory first and the maker’s own specs for the rest, and work out the room size it really cleans. On YouTube we explain where marketing claims and real performance part ways.
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