CADR stands for Clean Air Delivery Rate and measures how quickly an air purifier can remove dust, smoke, and pollen from your indoor air. The higher the CADR number, the faster and more effectively the purifier cleans your room—with ratings ranging from 10 to 450 cubic feet per minute (CFM). Understanding CADR helps you choose the right air purifier size for your space, ensuring you breathe cleaner air without wasting money on oversized units or struggling with underpowered ones.
Whether you’re battling allergies, concerned about indoor air quality, or shopping for your first air purifier, this guide explains everything about CADR ratings. You’ll learn how to calculate the ideal CADR for your room, understand rating charts, and discover what constitutes a good CADR rating for different spaces.
CADR, or Clean Air Delivery Rate, represents the volume of filtered air an air purifier delivers per minute. Developed by the Association of Home Appliance Manufacturers (AHAM) in the 1980s, this standardized metric helps consumers compare air purifier performance objectively.
The CADR rating essentially combines two crucial factors: airflow rate and filtration efficiency. If an air purifier moves 200 CFM of air with 100% filtration efficiency, its CADR would be 200. This single number tells you more about real-world performance than marketing claims about room coverage or filter types alone.
Think of CADR like a car’s miles-per-gallon rating—it provides a standardized way to compare different models regardless of brand or price. Without CADR, you’d be left guessing whether a purifier actually cleans air effectively or just moves it around.
Every AHAM-certified air purifier displays three separate CADR ratings, each measuring effectiveness against different particle sizes:
Smoke CADR (0.09-1.0 microns): Tests the smallest and most dangerous particles, including tobacco smoke, smog, and cooking fumes. These particles penetrate deepest into your lungs, making smoke CADR particularly important for health-conscious buyers.
Dust CADR (0.5-3.0 microns): Measures removal of medium-sized particles like dust mites, pet dander, and mold spores. This rating matters most for general household cleaning and allergen reduction.
Pollen CADR (5-11 microns): Evaluates performance against larger particles including pollen, lint, and carpet fibers. While these particles are less harmful, they’re common allergen triggers.
The maximum CADR ratings are 450 CFM for smoke and pollen, and 400 CFM for dust. These limits only affect testing of industrial-grade purifiers, as most residential units fall well below these thresholds.
Understanding what constitutes a good CADR rating depends entirely on your room size and air quality needs. Here’s a comprehensive breakdown:
| Room Size | Minimum CADR | Good CADR | Excellent CADR | Best For |
| Small (up to 150 sq ft) | 100 CFM | 150 CFM | 200+ CFM | Bedrooms, offices |
| Medium (150-300 sq ft) | 150 CFM | 225 CFM | 300+ CFM | Living rooms, master bedrooms |
| Large (300-500 sq ft) | 250 CFM | 350 CFM | 400+ CFM | Open floor plans |
| Extra Large (500+ sq ft) | 350 CFM | 450 CFM | Multiple units | Great rooms, basements |
For severe allergies or areas with high pollution, match the CADR to your room’s square footage rather than using the two-thirds rule. This ensures maximum air cleaning power when you need it most.
Calculating the right CADR for your room involves simple math but delivers powerful results. Follow these steps to determine your ideal clean air delivery rate:
Step 1: Measure Your Room Calculate square footage by multiplying length times width. For a 12×15 foot bedroom, that’s 180 square feet.
Step 2: Apply the AHAM Two-Thirds Rule Multiply your square footage by 0.67 (two-thirds). For our 180 square foot example: 180 × 0.67 = 120 CFM minimum CADR.
Step 3: Adjust for Ceiling Height Standard calculations assume 8-foot ceilings. Add 25% for 10-foot ceilings or 50% for 12-foot ceilings. Cathedral ceilings may require doubling the CADR requirement.
Step 4: Consider Your Specific Needs For wildfire smoke or severe allergies, use a 1:1 ratio (CADR equals square footage). For light use or occasional odors, the standard two-thirds ratio suffices.
While CADR numbers provide valuable comparisons, understanding their real-world implications helps you make better purchasing decisions. A purifier with 300 CADR doesn’t just move 300 cubic feet of air—it delivers 300 cubic feet of completely clean air every minute.
This distinction matters because raw airflow (CFM) doesn’t account for filtration efficiency. A fan might move 500 CFM but remove zero pollutants, giving it a CADR of 0. Conversely, a smaller unit with excellent HEPA filtration might achieve higher CADR despite lower airflow.
Most quality air purifiers achieve CADR ratings between 60-80% of their maximum airflow. If you see CADR numbers matching or exceeding stated airflow, be skeptical—this likely indicates measurement errors or misleading specifications.
Different rooms require different CADR levels based on their use, occupancy, and pollution sources. Here’s what experts recommend:
Bedrooms: Aim for 150-300 CADR to ensure multiple air changes during 8 hours of sleep. Higher CADR allows running on quieter, lower speeds at night while maintaining effectiveness.
Living Areas: Target 200-400 CADR to handle increased activity, multiple occupants, and varied pollution sources. Open floor plans may require multiple units or commercial-grade models.
Home Offices: 100-200 CADR suffices for smaller spaces under 150 square feet. Position the unit near your workspace for maximum benefit during long work sessions.
Kitchens: Choose 250+ smoke CADR specifically, as cooking generates fine particles. The smoke rating matters more than dust or pollen CADR in cooking areas.
A good CADR rating meets or exceeds the two-thirds rule for your room size while operating quietly enough for comfortable living. However, “good” varies by situation:
For General Use: Any CADR meeting the two-thirds rule (room square footage × 0.67) provides adequate air cleaning for healthy individuals in normal conditions.
For Allergies: Target CADR equal to 80-100% of room square footage. This ensures rapid allergen removal and maintains consistently clean air.
For Medical Needs: Consult healthcare providers, but generally aim for the highest CADR possible. Multiple air changes per hour become crucial for respiratory conditions.
For Pets: Focus on dust CADR ratings above 200, as pet dander falls within the dust particle size range. Pet-friendly plants can complement air purification efforts.
Beyond raw CADR numbers, several features affect real-world performance and satisfaction:
Multiple Fan Speeds: High CADR ratings typically reflect maximum speed performance. Ensure your chosen model maintains decent CADR on lower, quieter settings for nighttime use.
Filter Quality: True HEPA filters deliver consistent CADR performance. Lower-grade filters may test well initially but degrade quickly, reducing effective CADR over time.
Noise Levels: The highest CADR often comes with excessive noise. Balance cleaning power with livability—a slightly lower CADR running continuously beats a loud unit you’ll turn off.
Energy Efficiency: Energy Star certified models deliver high CADR while minimizing electricity costs. Look for units achieving at least 2.0 CADR per watt for optimal efficiency.
While CADR provides valuable standardized comparisons, it has important limitations to consider:
New Filter Testing: CADR reflects brand-new filter performance. Real-world efficiency drops 15-20% as filters accumulate particles over months of use.
Particle-Only Measurement: CADR doesn’t evaluate gas, odor, or chemical removal. Units with activated carbon may excel at odor control despite modest CADR ratings.
Maximum Speed Testing: Published CADR assumes continuous high-speed operation. Actual performance on quieter settings may be 30-50% lower.
Small Chamber Testing: The 1,008 cubic foot test chamber doesn’t replicate large rooms or homes with multiple air exchanges between spaces.
Understanding how CADR relates to other specifications helps you evaluate air purifiers comprehensively:
CADR vs. CFM: While CFM measures total airflow, CADR measures clean airflow. A 300 CFM unit might only achieve 200 CADR due to filter efficiency losses.
CADR vs. ACH: Air Changes per Hour depends on both CADR and room size. Higher CADR enables more ACH, but room volume ultimately determines the relationship.
CADR vs. MERV: MERV ratings evaluate filter efficiency, while CADR measures overall system performance. High MERV filters may restrict airflow, potentially lowering CADR.
CADR vs. Coverage Claims: Manufacturer coverage areas often assume minimal air changes. Always verify using CADR calculations rather than trusting marketing claims.
Selecting the right CADR involves balancing performance, price, and practical considerations. Start with the two-thirds rule as your baseline, then adjust based on specific needs.
Remember that two smaller units often outperform one large unit for the same total CADR. Multiple purifiers provide better air circulation and allow targeted placement near pollution sources.
Consider future needs too—choosing slightly higher CADR provides headroom for larger spaces or deteriorating outdoor air quality. The small additional cost typically pays off through years of better performance.
Most importantly, verify CADR ratings through AHAM’s directory or Energy Star databases. Independent certification ensures accurate ratings you can trust for protecting your indoor environment.
Understanding CADR ratings empowers you to choose air purifiers based on measurable performance rather than marketing hype. For most rooms, multiply square footage by 0.67 to find minimum CADR requirements. Adjust upward for allergies, pets, or high ceilings.
Focus on smoke CADR for the smallest particles, dust CADR for allergens, and pollen CADR for seasonal concerns. Balance high CADR with acceptable noise levels and energy efficiency for long-term satisfaction.
Ready to breathe cleaner air? Use these CADR guidelines to find the perfect air purifier for every room in your home. Your lungs will thank you for making an informed, science-based decision.
For more insights on improving your indoor environment, explore our guides on running your air purifier effectively and avoiding ionic air purifier risks.
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