CADR Explained: The Ultimate Guide
Master Clean Air Delivery Rate (CADR) ratings to choose the perfect air purifier for your needs
Quick Answer: What is CADR?
CADR (Clean Air Delivery Rate) measures how many cubic feet of air an air purifier can clean per minute. It's tested for three particle sizes: Smoke (0.09-1.0 μm), Dust (0.5-3.0 μm), and Pollen (5.0-11.0 μm). Higher CADR numbers mean faster air cleaning. For room sizing, use the 2/3 rule: CADR should be at least 2/3 of your room's square footage.
Table of Contents
What is CADR and Why It Matters
Clean Air Delivery Rate (CADR) is the gold standard for measuring air purifier performance. Developed by the Association of Home Appliance Manufacturers (AHAM), CADR provides an objective, standardized way to compare how effectively different air purifiers clean the air.
Key CADR Facts:
- Measured in CFM (Cubic Feet per Minute) or m³/h (cubic meters per hour)
- Three separate ratings: Smoke, Dust, and Pollen
- Ranges typically from 10 to 450 CFM for residential units
- AHAM Verifide certification ensures accuracy
Why CADR is Critical for Air Purifier Selection
Unlike marketing claims or proprietary ratings, CADR provides a standardized, third-party verified measurement that allows true apples-to-apples comparisons between air purifiers. This matters because:
Objective Performance Metric
CADR eliminates guesswork by providing concrete numbers based on standardized testing protocols, not manufacturer claims.
Room Size Matching
CADR directly correlates to the room size an air purifier can effectively clean, making sizing decisions straightforward.
Performance vs Price
Compare CADR per dollar to find the best value air purifiers that deliver real cleaning power, not just features.
Allergen-Specific Performance
Three separate ratings help you choose based on your specific concerns: smoke, dust mites, or pollen allergies.
The Science Behind CADR
CADR represents the volume of air that has been cleaned of a specific particle size per minute. It's calculated using this formula:
CADR = (Particle Decay Rate with Purifier - Natural Decay Rate) × Room Volume
This calculation accounts for both the air purifier's filtration efficiency AND its airflow rate, providing a complete picture of cleaning performance. A purifier with 99.97% HEPA efficiency but low airflow may have lower CADR than one with 99% efficiency but higher airflow.
How CADR is Measured and Tested
CADR testing follows the rigorous ANSI/AHAM AC-1 standard, ensuring consistent and reliable results across all certified air purifiers.
The AHAM Testing Protocol
Test Chamber Specifications:
- Size:1,008 cubic feet (28.5 m³) - equivalent to a 10' × 12' room with 8.4' ceilings
- Temperature:Maintained at 70°F ± 5°F (21°C ± 3°C)
- Humidity:40% ± 5% relative humidity
- Air Circulation:Ceiling fan ensures uniform particle distribution
Testing Process Step-by-Step
Baseline Measurement
Natural particle decay rate is measured without the air purifier running to establish baseline.
Particle Introduction
Test particles (cigarette smoke, Arizona road dust, or paper mulberry pollen) are introduced to specified concentrations.
Purifier Operation
Air purifier runs at maximum speed for 20 minutes (10 minutes for smoke).
Particle Counting
Particle concentrations measured at 2-minute intervals using laser particle counters.
CADR Calculation
Decay rates are analyzed and CADR values calculated for each particle size.
AHAM Verifide Certification
The AHAM Verifide program provides independent verification of CADR ratings. Certified products undergo:
Initial Testing
Independent lab testing to verify manufacturer claims
Annual Verification
Yearly retesting to ensure continued compliance
Random Testing
Unannounced market surveillance testing
Energy Testing
Energy efficiency ratings at different speeds
Understanding CADR Ratings (Smoke, Dust, Pollen)
CADR provides three separate ratings because different particles require different filtration approaches. Understanding these ratings helps you choose the right purifier for your specific air quality concerns.
| Particle Type | Size Range | What It Represents | Typical CADR Range |
|---|---|---|---|
| Smoke | 0.09 - 1.0 μm | Cigarette smoke, cooking odors, smog, viruses | 10 - 450 CFM |
| Dust | 0.5 - 3.0 μm | Dust mites, pet dander, fine dust, bacteria | 10 - 400 CFM |
| Pollen | 5.0 - 11.0 μm | Tree/grass pollen, mold spores, large dust | 10 - 450 CFM |
Smoke CADR: The Toughest Test
Why Smoke CADR is Often Lowest:
- • Smallest particle size (0.09-1.0 microns) requires finest filtration
- • Tests both HEPA efficiency and activated carbon for odor removal
- • Critical for wildfire smoke, cigarette smoke, and cooking odors
- • Best indicator of overall filtration capability
Dust CADR: The Allergen Fighter
What Dust CADR Tells You:
- • Performance against dust mites and pet dander
- • Effectiveness for general household dust
- • Usually middle value of the three ratings
- • Key metric for allergy sufferers
Pollen CADR: Large Particle Performance
Understanding Pollen CADR:
- • Typically the highest CADR value
- • Larger particles are easier to capture
- • Essential for seasonal allergy relief
- • Indicates mold spore removal capability
Real-World CADR Examples
Small Room Purifier
Example: Levoit Core 300
Medium Room Purifier
Example: Coway AP-1512HH
Large Room Purifier
Example: Blueair Blue Pure 211+
CADR to Room Size Calculator and Charts
The relationship between CADR and room size determines how effectively an air purifier can clean your space. Use our guidelines and calculators to find the perfect match.
The 2/3 Rule (AHAM Standard)
AHAM's Official Formula:
This provides 4.8 air changes per hour (ACH) in a room with 8-foot ceilings, suitable for general air cleaning.
CADR Requirements by Room Size
| Room Size | Square Feet | Minimum CADR | Recommended CADR | High Performance |
|---|---|---|---|---|
| Small Bedroom | 100 sq ft | 67 CFM | 100 CFM | 150+ CFM |
| Medium Bedroom | 150 sq ft | 100 CFM | 150 CFM | 225+ CFM |
| Master Bedroom | 200 sq ft | 133 CFM | 200 CFM | 300+ CFM |
| Living Room | 300 sq ft | 200 CFM | 300 CFM | 450+ CFM |
| Large Living | 400 sq ft | 267 CFM | 400 CFM | 600+ CFM |
| Open Concept | 500 sq ft | 333 CFM | 500 CFM | 750+ CFM |
| Whole Floor | 750 sq ft | 500 CFM | 750 CFM | 1000+ CFM |
| Large Space | 1000 sq ft | 667 CFM | 1000 CFM | 1500+ CFM |
Adjusting CADR for Special Situations
Increase CADR by 50% for:
- Heavy pollution or wildfire smoke
- Multiple pets or severe allergies
- Smoking indoors
- High ceilings (>9 feet)
Standard CADR Works for:
- Normal indoor air quality
- 8-foot ceilings
- Mild seasonal allergies
- General dust control
CADR vs CFM, ACH, and Other Metrics
While CADR is the gold standard, understanding how it relates to other air purifier metrics helps you make more informed decisions.
| Metric | What It Measures | Pros | Cons |
|---|---|---|---|
| CADR | Clean air volume per minute | Standardized, verified, accounts for efficiency | Limited to 450 CFM testing |
| CFM | Total airflow volume | Simple to understand | Doesn't account for filter efficiency |
| ACH | Air changes per hour | Room-specific measurement | Requires room size calculation |
| MERV | Filter efficiency rating | Standardized filter rating | Doesn't indicate airflow |
| Coverage Area | Maximum room size | Easy for consumers | Often inflated by manufacturers |
Understanding the Relationships
Key Formulas:
Why CADR Beats Raw CFM
Example: High CFM, Low Efficiency
- • CFM: 500
- • Filter Efficiency: 60%
- • Effective CADR: ~300 CFM
- • Result: Less clean air delivered
Example: Lower CFM, High Efficiency
- • CFM: 350
- • Filter Efficiency: 99.97%
- • Effective CADR: ~350 CFM
- • Result: More clean air delivered
When to Use Each Metric
Use CADR when:
Comparing different air purifier models or determining room size compatibility
Use ACH when:
Determining if air cleaning frequency meets health requirements (CDC recommends 5+ ACH)
Use CFM when:
Calculating ventilation requirements or comparing fan specifications
Use MERV when:
Selecting replacement filters or understanding filtration capability
How to Choose the Right CADR for Your Needs
Selecting the right CADR involves more than just room size. Consider your specific air quality concerns, health conditions, and usage patterns.
Step-by-Step CADR Selection Guide
Measure Your Room
Calculate square footage (length × width). For open floor plans, consider total area or use multiple units.
Apply Base Formula
Minimum CADR = Square Footage × 2/3. This gives you the baseline requirement.
Identify Primary Concern
Choose which CADR rating matters most: Smoke (odors/fine particles), Dust (allergens), or Pollen (seasonal allergies).
Adjust for Conditions
Add 25-50% for allergies, pets, pollution. Add 50-100% for smoking or severe conditions.
Consider Noise Levels
Higher CADR on lower speeds = quieter operation. Oversizing allows running on medium/low settings.
CADR Requirements by Use Case
Bedroom (Sleep)
150-200 sq ft room
- • Minimum: 100 CADR
- • Recommended: 150-200 CADR
- • Priority: Low noise operation
- • Best for: Allergen removal while sleeping
Home Office
100-150 sq ft room
- • Minimum: 75 CADR
- • Recommended: 100-150 CADR
- • Priority: Dust/particle removal
- • Best for: Concentration & productivity
Living Room
300-400 sq ft room
- • Minimum: 200 CADR
- • Recommended: 300-400 CADR
- • Priority: High volume cleaning
- • Best for: Family gatherings
Kitchen Area
150-250 sq ft room
- • Minimum: 150 CADR
- • Recommended: 200-300 CADR
- • Priority: Smoke CADR rating
- • Best for: Cooking odors/smoke
Allergy Sufferer
Any room size
- • Minimum: Room size × 1.0
- • Recommended: Room size × 1.5
- • Priority: Dust/Pollen CADR
- • Best for: Maximum relief
Pet Owner
Any room size
- • Minimum: Room size × 0.8
- • Recommended: Room size × 1.2
- • Priority: Dust CADR rating
- • Best for: Dander & fur control
Pro Tips for CADR Selection
- Oversizing is Better: A higher CADR unit running on low is quieter and more efficient than a small unit on high.
- Multiple Units: Two 200 CADR units often outperform one 400 CADR unit for large spaces.
- Speed Settings: Check CADR at different speeds - you'll likely use medium/low most often.
- Seasonal Needs: Consider your worst air quality season when selecting CADR.
CADR Limitations and What It Doesn't Tell You
While CADR is invaluable for comparing air purifiers, understanding its limitations helps you make fully informed decisions and set realistic expectations.
Key CADR Limitations
Testing Cap at 450 CFM
AHAM testing maxes out at 450 CFM, so industrial or whole-house units may show artificially capped ratings despite higher actual performance.
Maximum Speed Only
CADR is measured at the highest fan speed, which may be too loud for everyday use. Real-world performance on quieter settings is lower.
No Gas or VOC Testing
CADR doesn't measure removal of gases, VOCs, or odors. Units with activated carbon aren't reflected in CADR scores.
20-Minute Test Duration
Short test duration doesn't reveal long-term performance degradation or how quickly filters clog in real-world conditions.
Laboratory Conditions
Testing in controlled chambers doesn't account for real-world factors like air currents, humidity variations, or continuous pollution sources.
What CADR Doesn't Measure
Performance Factors Not in CADR:
- • Noise levels at different speeds
- • Energy consumption and efficiency
- • Filter replacement costs
- • Smart features or air quality sensors
- • Durability and build quality
- • Coverage pattern and air distribution
Pollutants Not Tested:
- • Viruses and bacteria (though captured)
- • Formaldehyde and VOCs
- • Radon gas
- • Carbon monoxide
- • Ultrafine particles (<0.09 μm)
- • Specific allergens (cat dander vs dust)
Beyond CADR: Additional Factors to Consider
Filter Longevity
Consider replacement frequency and costs. Some high-CADR units have expensive filters needing frequent changes.
Energy Star Rating
CADR per watt indicates efficiency. Energy Star certified units deliver high CADR with lower power consumption.
Real User Reviews
Complement CADR data with user experiences regarding noise, reliability, and real-world performance.
The Bottom Line on CADR Limitations
CADR remains the best standardized metric for air purifier performance, but it's one piece of the puzzle. Use CADR as your primary selection criteria, then consider noise levels, operating costs, and specific features that matter for your situation. A balanced approach ensures you get an air purifier that performs well on paper and in your actual living space.
Top CADR Air Purifiers by Room Size (2025)
Based on AHAM-verified CADR ratings and real-world performance, here are the top air purifiers for different room sizes in 2025.
Small Rooms (100-200 sq ft)
Levoit Core 300
Best ValueCADR Ratings:
S: 141 | D: 145 | P: 141
Coverage:
219 sq ft
Price Range:
$80-100
Coway AP-1512HH
Top PickCADR Ratings:
S: 234 | D: 248 | P: 240
Coverage:
361 sq ft
Price Range:
$150-230
Medium Rooms (200-400 sq ft)
Winix 5500-2
Best ValueCADR Ratings:
S: 232 | D: 243 | P: 246
Coverage:
360 sq ft
Price Range:
$130-160
Levoit Core 400S
Smart PickCADR Ratings:
S: 260 | D: 260 | P: 260
Coverage:
403 sq ft
Price Range:
$180-220
Large Rooms (400-600 sq ft)
Blueair Blue Pure 211+
Top PerformanceCADR Ratings:
S: 350 | D: 350 | P: 350
Coverage:
540 sq ft
Price Range:
$230-300
Coway Airmega 400
Premium ChoiceCADR Ratings:
S: 350 | D: 340 | P: 350
Coverage:
624 sq ft
Price Range:
$450-550
Frequently Asked Questions About CADR
What does CADR stand for?
CADR stands for Clean Air Delivery Rate. It's a standardized measurement developed by the Association of Home Appliance Manufacturers (AHAM) that indicates the volume of filtered air an air purifier delivers per minute, measured in cubic feet per minute (CFM).
Is higher CADR always better?
Generally yes, but context matters. Higher CADR means more air cleaning power, but it often comes with increased noise and energy consumption. The key is matching CADR to your room size. Oversizing slightly is beneficial as it allows quieter operation on lower speeds while still maintaining effective cleaning.
How do I calculate the CADR I need for my room?
Use the AHAM's 2/3 rule: Minimum CADR = Room Square Footage × 2/3. For example, a 300 sq ft room needs at least 200 CADR. For enhanced performance, especially with allergies or pets, multiply your square footage by 1.0 or even 1.5.
Use our Room Size to CADR Calculator →What's the difference between CADR and CFM?
CFM (Cubic Feet per Minute) measures total airflow, while CADR measures clean air delivery. CADR accounts for both airflow AND filtration efficiency. A unit with 500 CFM but 60% efficiency would have a CADR around 300 CFM, while a 350 CFM unit with 99.97% HEPA efficiency would have nearly 350 CADR.
Why are there three different CADR numbers?
The three CADR ratings (Smoke, Dust, Pollen) represent different particle sizes. Smoke (0.09-1.0 μm) tests fine particle filtration, Dust (0.5-3.0 μm) covers allergens like pet dander, and Pollen (5.0-11.0 μm) measures large particle removal. Different filters perform differently across particle sizes, so three ratings provide a complete performance picture.
Does CADR measure virus and bacteria removal?
CADR doesn't specifically test for viruses or bacteria, but the smoke CADR (0.09-1.0 μm) covers the size range of many viruses (0.02-0.3 μm) and bacteria (0.5-5.0 μm). A high smoke CADR indicates good performance against airborne pathogens, though it's not a direct measurement.
What is AHAM Verifide certification?
AHAM Verifide is an independent certification program that verifies manufacturers' CADR claims through third-party testing. Certified products undergo initial testing, annual verification, and random market surveillance to ensure ongoing compliance. Look for the AHAM Verifide seal when shopping for air purifiers.
Can CADR decrease over time?
Yes, CADR decreases as filters become clogged with particles. Most air purifiers lose 10-30% of their CADR over 6-12 months of use. Regular filter replacement according to manufacturer guidelines is essential to maintain rated CADR performance. Some units have filter indicators to alert you when replacement is needed.
What's a good CADR for wildfire smoke?
For wildfire smoke, focus on the Smoke CADR rating and size up by 50-100%. For a 200 sq ft room, aim for 200-300 Smoke CADR instead of the standard 133 CADR. The EPA recommends creating a "clean room" with the highest CADR unit you can find during smoke events. Multiple units may be necessary for severe conditions.
Do all air purifiers have CADR ratings?
No, not all air purifiers have CADR ratings. Only models tested according to AHAM standards receive CADR ratings. Some manufacturers choose not to test (often because their units wouldn't score well), while others use proprietary metrics. Be skeptical of purifiers without CADR ratings, as they lack standardized performance verification.
Ready to Find Your Perfect Air Purifier?
Now that you understand CADR ratings, use our tools and guides to find the ideal air purifier for your needs.
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