What Is CADR Rating? (Clean Air Delivery Rate Explained)
CADR stands for Clean Air Delivery Rate. It's a standardized metric that measures the volume of filtered air an air purifier delivers, expressed in cubic feet per minute (CFM). The standard was developed by AHAM and codified as ANSI/AHAM AC-1, first published in 1988 and last revised in 2020.
Here's the key formula that makes CADR so useful:
CADR = Airflow (CFM) × Filter Efficiency
This means CADR captures both how much air a purifier moves and how well the filter actually removes particles. A purifier with a massive fan but a mediocre filter will have a lower CADR than one with a HEPA filter and a moderately powerful fan.
Testing takes place in a sealed 1,008 ft³ chamber (10.5 ft × 12 ft × 8 ft) over a 20-minute test period. Pollutants are released, the purifier runs, and scientists measure how quickly particle concentrations drop compared to the natural decay rate when the purifier is off. The EPA, FTC, ENERGY STAR, and Consumer Reports all recognize CADR as the standard air purifier performance metric.
The Three CADR Measurements: Smoke, Dust, and Pollen
Every AHAM-verified air purifier is tested against three specific particle types. Each represents a different size range of common indoor pollutants:
| Particle Type | Size Range | Represents | Max Rated CADR |
|---|
| Smoke | 0.09-1.0 μm | Tobacco/wildfire smoke, cooking fumes, fine PM2.5, some bacteria | 450 CFM |
| Dust | 0.5-3.0 μm | Household dust, dust mites, pet dander, fine particulates | 400 CFM |
| Pollen | 5.0-11.0 μm | Pollen grains, mold spores, large allergens | 550 CFM |
Smoke particles are the smallest and hardest to filter. That's exactly why AHAM uses the smoke CADR for room sizing — if a purifier can handle smoke effectively, it can handle everything larger. The EPA confirms this: to target fine particulate matter (PM2.5), choose a purifier with a high smoke CADR.
CADR Units and How AHAM Testing Works (ANSI/AHAM AC-1)
CADR is measured in CFM (cubic feet per minute) in the United States. Some manufacturers — particularly those selling internationally — report CADR in m³/h (cubic meters per hour). Watch out for this: 1 CFM = 1.699 m³/h, so metric CADR numbers look artificially inflated.
The AHAM Verifide® certification program is voluntary. An independent lab randomly selects and tests models to confirm manufacturers' CADR claims. Look for the AHAM Verifide seal on the box — it lists all three CADR numbers plus the recommended room size.
A note on limitations: CADR only measures particle filtration. It does not measure removal of gases, VOCs, or odors. It's also tested with a brand-new filter at maximum fan speed — your real-world CADR on medium speed with a 3-month-old filter will be lower.
CADR Rating Chart — What Is a Good CADR Rating?
What is a good CADR rating for an air purifier? It depends entirely on your room size. A CADR of 150 is excellent for a small bedroom but inadequate for a 400 sq ft living room.
The chart below maps CADR ranges to room size coverage, quality tiers, and typical use cases. This is the core reference table for the entire article:
| Smoke CADR (CFM) | Room Size (sq ft) | ACH Delivered | Quality Tier | Typical Use |
|---|
| 50-100 | 78-155 sq ft | 4.8 ACH | Low | Personal space, small office |
| 100-150 | 155-233 sq ft | 4.8 ACH | Low—Medium | Small bedroom, dorm room |
| 150-200 | 233-310 sq ft | 4.8 ACH | Medium | Standard bedroom, home office |
| 200-300 | 310-465 sq ft | 4.8 ACH | Good | Living room, master bedroom |
| 300-400 | 465-620 sq ft | 4.8 ACH | High | Large room, open floor plan |
| 400+ | 620+ sq ft | 4.8 ACH | Excellent | Great room, loft, commercial |
Room sizes are calculated using AHAM's official formula: Room Size (sq ft) = Smoke CADR × 1.55. This assumes standard 8-foot ceilings. If your ceilings are taller (9-10 ft), size up to the next CADR tier.
For most homeowners, a CADR of 200-300 hits the sweet spot — enough to clean a typical living room or large bedroom without excessive noise or energy consumption. You can learn more about matching a purifier to your specific space in our air purifier sizing guide.
AHAM's 2/3 Rule for Room Sizing
AHAM recommends a simple rule of thumb: your air purifier's smoke CADR should equal at least 2/3 of the room's floor area in square feet. This ensures the purifier delivers a minimum of 4.8 air changes per hour (ACH) and removes at least 80% of smoke particles.
Example: A 300 sq ft living room needs a minimum smoke CADR of 300 × 2/3 = 200 CFM. A 450 sq ft open-plan space needs at least 300 CFM.
For wildfire smoke: AHAM recommends a higher standard — your smoke CADR should equal your room's full square footage (not just 2/3). So that 300 sq ft room needs a CADR of 300, not 200. If you live in a wildfire-prone area, this is critical when checking where to place your air purifier for maximum coverage.
How to Read a CADR Label: Smoke, Dust, and Pollen Ratings
The AHAM Verifide seal on air purifier packaging displays three CADR numbers listed in a specific order: smoke, dust, pollen. This order goes from smallest to largest particles — and from most to least dangerous.
Here's how to read a typical label:
| Label Line | Example Value | What It Tells You |
|---|
| Smoke CADR | 240 CFM | How well it handles fine particles (PM2.5). Used for room sizing. |
| Dust CADR | 250 CFM | How well it handles mid-size particles like household dust and pet dander. |
| Pollen CADR | 260 CFM | How well it handles large allergens. Usually the highest number. |
| Suggested Room Size | 372 sq ft | Calculated from Smoke CADR × 1.55. Based on 4.8 ACH. |
Which CADR Number Matters Most for Your Needs?
For general use and room sizing, the smoke CADR is your primary metric. It tests against the smallest, hardest-to-filter particles.
However, if you have a specific concern, prioritize accordingly. If you suffer from seasonal allergies, pay special attention to the pollen CADR. If pet dander is your main issue, the dust CADR matters most. We'll cover use-case recommendations in detail below.
If all three numbers are close together (within 10-20% of each other), that's a sign of a well-balanced purifier with a high-quality filter. A HEPA filter typically delivers near-identical scores across all three categories because it captures 99.97% of particles at 0.3 μm. You can learn more about how HEPA filtration affects performance in our HEPA filter guide.
CADR vs CFM — Why They're Not the Same
This is one of the most common points of confusion. CFM (cubic feet per minute) measures raw airflow — how much air the fan can move. CADR measures how much clean air the device actually delivers after filtration.
| Metric | Measures | Accounts for Filter? | Who Tests It? |
|---|
| CFM | Total airflow through the device (fan output) | No — raw airflow only | Manufacturer-reported |
| CADR | Volume of filtered, particle-free air delivered | Yes — combines airflow × filter efficiency | AHAM (independent, third-party) |
CFM is always equal to or greater than CADR. A filter, even a brand-new one, reduces airflow. If a manufacturer lists CFM and CADR as identical — or the CADR as higher than CFM — that's a red flag.
Here's why this matters in practice:
| Scenario | Fan CFM | Filter Efficiency | Resulting Smoke CADR |
|---|
| HEPA filter (99.97%) | 200 CFM | 99.97% | ~200 CADR |
| MERV 14 filter (~80%) | 200 CFM | ~80% | ~160 CADR |
| MERV 12 filter (~40%) | 200 CFM | ~40% | ~80 CADR |
| Low-quality filter | 300 CFM | ~25% | ~75 CADR |
That last row is the important one. A purifier can advertise "300 CFM airflow!" but deliver a smoke CADR of only 75. CADR is the metric that tells you the truth. If you're comparing purifier specs to your HVAC system's output, our CFM calculator can help.
What Is a Good CADR Rating by Use Case?
Not everyone needs the same CADR. Your primary concern — allergies, smoke, dust, or large-room coverage — determines which CADR number to prioritize and how high it needs to be.
Best CADR for Allergies (Pollen CADR Most Important)
If seasonal allergies are your primary concern, focus on the pollen CADR. Pollen particles (5-11 μm) are the largest of the three types, so most purifiers score highest on this metric.
For a standard 250 sq ft bedroom, look for a pollen CADR of at least 170 CFM. For a 400 sq ft living room during peak allergy season, aim for 270+ CFM. A true HEPA filter will deliver excellent pollen removal — see our HEPA filter guide for details on filter grades.
Best CADR for Smoke and Wildfire (Smoke CADR Most Important)
For tobacco smoke, cooking smoke, or wildfire events, the smoke CADR is everything. Smoke particles are as small as 0.09 μm — tiny enough to penetrate deep into your lungs.
Under normal conditions, apply the 2/3 rule. For a 300 sq ft room, you need a smoke CADR of at least 200 CFM. During wildfire events, AHAM recommends upgrading to a smoke CADR that equals your room's full square footage (300 CFM for a 300 sq ft room).
Placement matters significantly for smoke removal. Our guide on where to place an air purifier covers optimal positioning for maximum CADR coverage.
Best CADR for Dust and Pet Dander (Dust CADR)
Household dust and pet dander fall in the 0.5-3.0 μm range — the mid-size category measured by dust CADR. If you have pets, live near a highway, or have forced-air HVAC that recirculates dust, pay attention to this number.
For a 300 sq ft room with one or two pets, aim for a dust CADR of at least 200 CFM. For heavy pet households or rooms with carpet, go higher — 250+ CFM. Your furnace filter also plays a major role here; check our MERV rating chart to understand how furnace filtration and purifier filtration complement each other.
Best CADR for Large Rooms (400+ sq ft)
Large rooms and open floor plans are where CADR really matters. Using the 2/3 rule:
| Room Size | Min Smoke CADR (2/3 Rule) | Min Smoke CADR (Wildfire) | ACH at Min CADR |
|---|
| 400 sq ft | 267 CFM | 400 CFM | 4.8 ACH |
| 500 sq ft | 333 CFM | 500 CFM | 4.8 ACH |
| 600 sq ft | 400 CFM | 600 CFM | 4.8 ACH |
| 700 sq ft | 467 CFM | 700 CFM | 4.8 ACH |
| 800 sq ft | 533 CFM | 800 CFM | 4.8 ACH |
For rooms above 600 sq ft, a single portable purifier often can't deliver enough CADR at reasonable noise levels. Consider using two smaller purifiers placed on opposite sides of the room, or supplementing with whole-house furnace filtration.
CADR and Air Changes per Hour (ACH) Relationship
Air Changes per Hour (ACH) measures how many times a purifier can filter the entire volume of air in a room within one hour. It's directly calculated from CADR:
ACH = (CADR × 60) ÷ Room Volume (ft³)
For a standard 8-foot ceiling, room volume is simply square footage × 8. Here's how different CADR levels translate to ACH in common room sizes:
| Room (sq ft) | Room Volume (ft³) | CADR 150 | CADR 200 | CADR 300 | CADR 400 |
|---|
| 150 sq ft | 1,200 ft³ | 7.5 ACH | 10.0 ACH | 15.0 ACH | 20.0 ACH |
| 200 sq ft | 1,600 ft³ | 5.6 ACH | 7.5 ACH | 11.3 ACH | 15.0 ACH |
| 300 sq ft | 2,400 ft³ | 3.8 ACH | 5.0 ACH | 7.5 ACH | 10.0 ACH |
| 400 sq ft | 3,200 ft³ | 2.8 ACH | 3.8 ACH | 5.6 ACH | 7.5 ACH |
| 500 sq ft | 4,000 ft³ | 2.3 ACH | 3.0 ACH | 4.5 ACH | 6.0 ACH |
| Organization | Recommended Min ACH | Context |
|---|
| AHAM | 4.8 ACH | Minimum for all Verifide-certified purifiers at suggested room size |
| CDC | 5.0 ACH | Recommended for workplaces |
| ASHRAE | 6.0 ACH | Recommended for schools and healthcare-adjacent spaces |
If you want to calculate ACH for your specific room, our air changes per hour guide walks through the math. The key takeaway: AHAM's 2/3 rule guarantees 4.8 ACH. If you need more (health concerns, smoke, COVID ventilation), size up your CADR.
Air Purifier Energy Consumption by CADR Level
Air purifiers are relatively low-energy appliances. Most use 30-100 watts on their highest setting — comparable to a ceiling fan or laptop charger. Based on data from 243 air purifiers analyzed by EcoCostSavings, the average efficiency is 4.6 CADR per watt.
| CADR Range | Typical Wattage (High) | Annual kWh (24/7) | Est. Annual Cost | ENERGY STAR Min |
|---|
| 50-100 CFM | 20-40W | 175-350 kWh | $28-$56 | 2.0 CADR/W |
| 100-200 CFM | 40-70W | 350-613 kWh | $56-$98 | 2.0 CADR/W |
| 200-300 CFM | 60-100W | 526-876 kWh | $84-$140 | 2.0 CADR/W |
| 300-450 CFM | 75-150W | 657-1,314 kWh | $105-$210 | 2.0 CADR/W |
Annual costs assume $0.16/kWh (U.S. average) and continuous 24/7 operation on high speed. In practice, most people run purifiers on medium or auto mode, which cuts energy use by 40-60%.
ENERGY STAR certified air purifiers must meet a minimum efficiency of 2.0 CADR per watt (dust). The most efficient models on the market achieve 6+ CADR per watt, delivering twice the clean air for the same energy input. ENERGY STAR certified purifiers are up to 56% more efficient than standard models. For comparison with your central system's efficiency, see our SEER rating and EER rating guides.
Dehumidifier Energy Efficiency — Energy Factor and IEF Explained
If you're researching air quality equipment, dehumidifier efficiency is closely related. Like CADR for air purifiers, the U.S. Department of Energy has standardized efficiency metrics for dehumidifiers. Understanding these helps you compare units and avoid overpaying on electricity.
What Is Energy Factor (EF) and Integrated Energy Factor (IEF)?
| Metric | Full Name | Units | Includes Standby Energy? | Status |
|---|
| EF | Energy Factor | L/kWh | No — active mode only | Replaced (pre-2019) |
| IEF | Integrated Energy Factor | L/kWh | Yes — active + standby + off mode | Current standard (since June 2019) |
IEF (Integrated Energy Factor) is the current standard. It measures how many liters of water a dehumidifier removes per kilowatt-hour of total energy consumed — including energy used during standby and off modes. Higher IEF = more efficient.
The DOE updated the test procedure in 2019 to test portable dehumidifiers at 65°F (previously 80°F) to better reflect basement conditions. This means newer models may show lower capacity ratings than older ones tested at 80°F, even though real-world performance hasn't changed.
Humidity management is a key part of indoor air quality. For more on how humidity affects your HVAC system, check our indoor humidity guide and our explainer on whether AC removes humidity.
ENERGY STAR Dehumidifier Certification Requirements
As of the Version 6.0 specification , ENERGY STAR certified dehumidifiers must meet these minimum IEF requirements:
Portable Dehumidifiers:
| Capacity (pints/day) | Minimum IEF (L/kWh) |
|---|
| ≤ 25.00 pints/day | ≥ 1.70 L/kWh |
| 25.01-50.00 pints/day | 2.01 L/kWh |
| ≥ 50.01 pints/day | ≥ 3.30 L/kWh |
Whole-Home Dehumidifiers:
| Case Volume (ft³) | Minimum IEF (L/kWh) |
|---|
| ≤ 8.0 ft³ | ≥ 2.22 L/kWh |
| > 8.0 ft³ | ≥ 3.81 L/kWh |
The top-performing dehumidifiers currently achieve IEF ratings of 1.95+ L/kWh for portable units and 2.35+ L/kWh for whole-home systems.
Dehumidifier Energy Consumption by Capacity
| Capacity | Typical Wattage | Est. Annual kWh | Est. Annual Cost | Best For |
|---|
| 20-25 pints/day | 300-400W | 350-500 kWh | $56-$80 | Small rooms, bathrooms |
| 30-40 pints/day | 400-550W | 500-700 kWh | $80-$112 | Bedrooms, moderate humidity |
| 50 pints/day | 500-600W | 600-750 kWh | $96-$120 | Basements, large rooms |
| 70+ pints/day | 600-800W | 700-1,000 kWh | $112-$160 | Severe humidity, whole-home |
Annual estimates assume 6-8 hours of daily operation during the dehumidification season (typically May—October). Running a dehumidifier continuously in a damp basement will increase costs by 50-80%.
Frequently Asked Questions About CADR Ratings
Is a higher CADR always better?
Higher CADR means faster, more effective filtration — but it comes with trade-offs. Higher-CADR purifiers use more energy and produce more noise on their top settings. The goal is to match your CADR to your room size using the 2/3 rule, not to buy the highest number available.
What does CADR 200 vs 300 vs 400 mean?
A CADR of 200 means the purifier delivers 200 CFM of particle-free air. Using the 2/3 rule, that covers about 310 sq ft. A CADR of 300 covers 465 sq ft, and 400 covers 620 sq ft. The bigger your room, the higher the CADR you need.
Does CADR measure bacteria and viruses?
The standard CADR test (ANSI/AHAM AC-1) only measures particle removal for smoke, dust, and pollen. However, AHAM has introduced new standards: AC-5-2022 measures microbiological CADR (m-CADR) for bacteria and viruses, and AC-4-2022 measures chemical CADR (c-CADR) for VOCs and gases. These are still relatively new and not yet widely adopted.
Can I compare CADR between different brands?
Yes — that's the whole point of CADR. It's a standardized, third-party-tested metric specifically designed for cross-brand comparison. Look for the AHAM Verifide seal to ensure the numbers were independently verified. Be cautious with brands that report only CFM or use m³/h instead of CFM (the metric numbers look inflated).
What if my air purifier doesn't have a CADR rating?
AHAM certification is voluntary, so some brands — particularly smaller or international ones — skip it. Without a verified CADR, you're relying on manufacturer claims about coverage area, which are often inflated. We strongly recommend choosing a purifier with an AHAM-verified CADR for any room over 150 sq ft.
How does CADR relate to MERV ratings on furnace filters?
CADR and MERV measure different things for different equipment. MERV rates a filter's efficiency at capturing particles of specific sizes. CADR rates a complete air purifier system (filter + fan + airflow design). A higher MERV furnace filter can complement a portable purifier by cleaning air throughout your entire duct system. See our MERV rating chart and furnace filter guide for details on whole-home filtration.