# Best Air Purifier Size for a Bedroom

_Last updated: 2026-09-26_

## Short answer

Size a bedroom purifier by smoke CADR, not by the "room size" on the box. For a standard 8 ft ceiling, a common target is a smoke CADR of at least two-thirds of the room's floor area in square feet, which is roughly five air changes per hour.

## The formula

- Air changes per hour (ACH) = CADR (CFM) x 60 / room volume (ft³).
- Room volume = floor area (ft²) x ceiling height (ft).
- For an 8 ft ceiling and a 5 ACH target, CADR ≈ floor area x 2/3.
- For allergy or open doors, target higher: CADR ≈ floor area or more.

## Worked examples

- 100 ft² bedroom, 8 ft ceiling: 100 x 2/3 ≈ 67 CFM minimum; 100 CFM for faster cleaning.
- 200 ft² bedroom: at least ~130 CFM; ~200 CFM if you want a strong margin.
- Open-plan area of 600 ft²: treat it as one space and target ~400 CFM or more.

## What else to weigh

- Noise at the speed you will run overnight, not just the sleep rating.
- Filter type: true HEPA plus carbon if odor matters.
- Filter cost and availability over a year.
- Sensor and auto mode, if you want it to react on its own.

## Common mistakes

- Trusting the box's "recommended room size" instead of CADR.
- Sizing one unit for several closed bedrooms.
- Ignoring noise until the unit is too loud to sleep next to.
- Forgetting that a dirty filter lowers effective airflow over time.

## Sources

U.S. EPA, Guide to Air Cleaners in the Home; AHRI Standard 680 (CADR definition); manufacturer CADR ratings. Verify current ratings before buying.

## Frequently asked questions

**Q: Is a higher CADR always better for a bedroom?**

A: It cleans faster, but it is usually louder and costs more to run and filter. Choose the CADR you need, then favour the quieter unit.

**Q: Should I size for the bedroom or the whole house?**

A: For sleep, size for the bedroom with the door closed. A whole-house figure assumes open doors and good mixing, which is not how bedrooms usually work at night.

**Q: How often should I run it?**

A: Keeping it on low continuously holds particle levels down; run a higher speed when you want faster cleaning, such as before bed.

## Recommended options

Once you know your target CADR, compare these models on noise at the speed you will actually use overnight.

- [DREO 530S Air Purifier (RGBIC)](https://www.amazon.com/dp/B0H8SB7YY1?maas=maas_adg_api_585602613512925350_static_12_201&ref_=aa_maas&tag=maas&aa_campaignid=PBd80bd4ce4ece40f44bcc76fcc0c48425&aa_adgroupid=99abOnP1pC8lf4AnvobrGKTnTfr_aKBQUZzDSUkZjocNFub_bs2frgjcI9NkRYC5C65ukTVHJxDAMQFHWlCkIH&aa_creativeid=8f82wlDYPds5P7ntLZtXI09xBlRY0rvWPPQ0azuMhEvyCLc_c) — DREO, rating 4.5/5 (555 reviews)
- [DREO DR-HAP009AS Pet Air Purifier](https://www.amazon.com/dp/B0H753GWC1?maas=maas_adg_api_585602613512925350_static_12_201&ref_=aa_maas&tag=maas&aa_campaignid=PBd80bd4ce4ece40f44bcc76fcc0c48425&aa_adgroupid=13ecG5KAMWcfJykf4pdfWcStqvzCgeCvqzsR_bcnGq2HJTblNA9W1GA6P7kEDkbx8ClHvhIZxYW6xXmBzqJL0&aa_creativeid=fff7QUdtMLEX_a2n4hsK10QP49ZRFN6OipmXUkpgLBAnLg9w_c) — DREO, rating 4.5/5 (555 reviews)
- [DREO DR-HAP009 Air Purifier](https://www.amazon.com/dp/B0HC2NW6QZ?maas=maas_adg_api_585602613512925350_static_12_201&ref_=aa_maas&tag=maas&aa_campaignid=PBd80bd4ce4ece40f44bcc76fcc0c48425&aa_adgroupid=80e5_baTqH7vY0Q1DRzuTL5Z1V3VvIGiJ_bxCUxy2rVJc1Q77oOqsvvyIUKmmperX_afCg1Sxsc84o3Xp6qsq11&aa_creativeid=e6a929APCR0MMPy8NbNGgZ5zHn6zK08Fd676nqYoO6INOgM_c) — DREO, rating 4.5/5 (555 reviews)

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