Air Purifier Size Calculator

Find the right CADR and purifier size based on your room dimensions and air changes per hour (ACH).

List of the Top 10 Best Air Purifier:

# Image Product Link
1 BLUEAIR Air Purifiers for Large Rooms, Cleans 3,048 Sqft In One Hour, HEPASilent Smart Air Cleaner For Home, Pets, Allergies, Virus, Dust, Mold, Smoke - Blue Pure 211i Max BLUEAIR Air Purifiers for Large Rooms, Cleans 3,048 Sqft In One Hour, HEPASilent Smart Air Cleaner For Home, Pets, Allergies, Virus, Dust, Mold, Smoke - Blue Pure 211i Max View on Amazon
2 Coway Airmega AP-1512HH(W) True HEPA Purifier with Air Quality Monitoring, Auto, Timer, Filter Indicator, and Eco Mode, 16.8 x 18.3 x 9.7, White Coway Airmega AP-1512HH(W) True HEPA Purifier with Air Quality Monitoring, Auto, Timer, Filter Indicator, and Eco Mode, 16.8 x 18.3 x 9.7, White View on Amazon
3 LEVOIT Air Purifier for Home Allergies Pet Hair in Bedroom, Covers Up to 1074 ft² by 56W High Torque Motor, AHAM VERIFIDE, 3-in-1 Filter with HEPA Sleep Mode, Remove Dust Smoke Odor, Core300-P, White LEVOIT Air Purifier for Home Allergies Pet Hair in Bedroom, Covers Up to 1074 ft² by 56W High Torque Motor, AHAM VERIFIDE, 3-in-1 Filter with HEPA Sleep Mode, Remove Dust Smoke Odor, Core300-P, White View on Amazon
4 Air Purifiers for Home Large Room up to 2400sq.ft, LUNINO H13 HEPA Air Filter with PM 2.5 Display Air Quality Sensors, Aromatherapy Function, Air Cleaner for Dust, Smoke, Dander, Pets Hair, Pollen Air Purifiers for Home Large Room up to 2400sq.ft, LUNINO H13 HEPA Air Filter with PM 2.5 Display Air Quality Sensors, Aromatherapy Function, Air Cleaner for Dust, Smoke, Dander, Pets Hair, Pollen View on Amazon
5 Jafända Air Purifier for Home Large Room 3800 ft², APP & Alexa, Ture HEPA Activated Carbon Air Filter, Smart HEPA Air Purifiers for Office Remove Dust Pollen Smoke Allergies Mold Odors Pet Dander VOCs Jafända Air Purifier for Home Large Room 3800 ft², APP & Alexa, Ture HEPA Activated Carbon Air Filter, Smart HEPA Air Purifiers for Office Remove Dust Pollen Smoke Allergies Mold Odors Pet Dander VOCs View on Amazon
6 Air Purifiers for Home Large Room 2200 Ft² with Washable Filters, MOOKA H13 HEPA Filter Pet Air Purifier for Bedroom with Fragrance, Air Cleaner for Smoke Dust Pollen Pets Hair Odor, KJ190L White Air Purifiers for Home Large Room 2200 Ft² with Washable Filters, MOOKA H13 HEPA Filter Pet Air Purifier for Bedroom with Fragrance, Air Cleaner for Smoke Dust Pollen Pets Hair Odor, KJ190L White View on Amazon
7 Air Purifiers for Home Large Room up to 2200sq.ft, MOOKA Air purifier for Home Pets with Washable Filter, PM 2.5 Display Air Quality Sensor Air Cleaner for Bedroom, Dorm room, Pets, Office, PR1 Air Purifiers for Home Large Room up to 2200sq.ft, MOOKA Air purifier for Home Pets with Washable Filter, PM 2.5 Display Air Quality Sensor Air Cleaner for Bedroom, Dorm room, Pets, Office, PR1 View on Amazon
8 LEVOIT Air Purifiers for Home Large Room Up to 1878 Ft² with Washable Pre-Filter, AHAM VERIFIDE, Air Quality Monitor, HEPA Sleep Mode for Allergies, Pet Hair in Bedroom, Vital 200S-P, White LEVOIT Air Purifiers for Home Large Room Up to 1878 Ft² with Washable Pre-Filter, AHAM VERIFIDE, Air Quality Monitor, HEPA Sleep Mode for Allergies, Pet Hair in Bedroom, Vital 200S-P, White View on Amazon
9 HATHASPACE HSP002 True HEPA Air Purifier for Home, Removes 99.9% of Dust, Smoke, Pet Dander, Odors, VOCs, Covers Up to 1500 Sq. Ft, Quiet Air Cleaner with Smart Sensor for Bedroom & Large Rooms HATHASPACE HSP002 True HEPA Air Purifier for Home, Removes 99.9% of Dust, Smoke, Pet Dander, Odors, VOCs, Covers Up to 1500 Sq. Ft, Quiet Air Cleaner with Smart Sensor for Bedroom & Large Rooms View on Amazon
10 GermGuardian Air Purifier for Home with HEPA Pure Filter, for Wildfire Smoke, Pet Dander, Pollen, Odors, Large Rooms Up To 743 Sq. Ft., Removes 99.97% Pollutants, UV-C Light, 22 GermGuardian Air Purifier for Home with HEPA Pure Filter, for Wildfire Smoke, Pet Dander, Pollen, Odors, Large Rooms Up To 743 Sq. Ft., Removes 99.97% Pollutants, UV-C Light, 22", AC4825E, Gray View on Amazon

How to Choose the Right Air Purifier Size

Selecting the correct air purifier for your space is vital for achieving optimal air quality. The key metric is the Clean Air Delivery Rate (CADR), which indicates how quickly an air purifier can remove particles from the air. Use this calculator to determine the ideal CADR rating based on your room size and how often you want the air cleaned (measured in Air Changes per Hour or ACH).

What Is CADR?

CADR stands for Clean Air Delivery Rate and is measured in cubic feet per minute (CFM). It tells you how much filtered air the purifier can deliver. A higher CADR means faster and more effective filtration.

What Is ACH?

ACH (Air Changes per Hour) refers to how many times the entire air volume of a room is filtered in one hour. For example:

  • 2 ACH – Suitable for minimal air quality issues
  • 4 ACH – Good for most households
  • 6 ACH – Ideal for allergy sufferers
  • 8+ ACH – Necessary for smokers, pets, or industrial settings

CADR Calculation Formula

CADR = (Room Volume × ACH) / 60

Where:

  • Room volume = Length × Width × Height (in cubic feet)
  • ACH = Number of air changes per hour
  • 60 = Number of minutes per hour

Example Calculation

Room: 15 × 12 × 8 ft → 1,440 ft³

Desired ACH: 6

CADR = (1,440 × 6) / 60 = 144 CFM

So you would need a purifier with at least a 144 CADR rating.

CADR Ratings by Room Size

Room Size (sq ft) Room Volume (ft³) ACH 4 ACH 6
150 1,200 80 CFM 120 CFM
300 2,400 160 CFM 240 CFM
500 4,000 267 CFM 400 CFM

Other Sizing Tips

  • Look for CADR ratings specifically for smoke, pollen, and dust
  • Avoid oversized purifiers that waste energy
  • Don’t forget about filter replacement cost and frequency

Common Questions

Q: Can I use a purifier in a larger room than rated?

A: It will work, but less effectively. The air may not be filtered fast enough to reduce allergens or odors efficiently.

Q: What CADR rating is good for asthma or allergies?

A: Look for a purifier with 6 ACH or more, and a CADR at least 2/3 of the room’s square footage.

Q: Is higher ACH always better?

A: More ACH equals faster purification, but may create more noise or drafts. Match it to your needs.

Conclusion

Choosing the right air purifier depends on your room size, air quality goals, and sensitivity to allergens. This calculator simplifies the math by giving you an accurate CADR recommendation based on your chosen ACH level. Use it to match your space with the right unit and breathe cleaner, healthier air.