CADR Rating Explained
CADR, the Clean Air Delivery Rate, is a metric that was developed as a way of measuring the performance of air purifiers for home. The CADR rating reflects the volume of air in CFM (cubic feet per minute) that is cleaned of particles of certain sizes.
To measure the effectiveness in removing different particle sizes, three types of particles are tested: smoke, pollen and dust. These represent small, medium and large sized particles. Each is measured and assigned it’s own CADR score. Starting in 2024, there is a new CADR metric called PM2.5 CADR. PM2.5 are particles smaller than 2.5 microns and PM2.5 CADR is roughly an average of the smoke and dust numbers.
CADR Certified Air Cleaners
The Association of Home Appliance Manufacturers (AHAM) oversees the CADR rating program. As part of this program, air cleaners are randomly selected and independently tested to confirm they continue to meet the performance levels.
Here is a screenshot of the mod and mod jr CADR ratings from the AHAM website.
Benefits Of CADR
The advantage of the CADR rating is that it gives the consumer a way to compare air purifiers that consider both air flow and filter efficiency. In other words, it provides a way to compare performance across products in a consistent way.
The CADR is basically a reflection of the air flow (CFM) times the efficiency of the air filter. So, if an air filter has 200 cfm and 100% efficiency the CADR would be 200. If the air filter has 200 cfm and 75% efficiency the CADR would be 150.
The CADR is a good way to keep from being misled in marketing messages.
For example, if a filter has a very high filter efficiency but low air flow the CADR helps to balance the two.
We see this commonly from some manufacturers that use particle counters to show the high efficiency of their air purifiers when selling to customers. This method can be very compelling as the shopper sees how well the particles are removed.
While this test is valid it does not factor in other important data points such as the air flow and noise level. Therefore it does not give you a complete picture for how well the air purifier will work in their environment.
Air Filtering Standard
The CADR is the standard in the US and is shown in CFM (cubic feet per minute). In Asia, CADR is in cubic meters per hour (m3/h).
Most air purifier brands show performance in CFM however some show m3/h in North America and this is misleading because the number is inflated.
For example, 235 CFM = 400 m3/h.
The AHAM CADR standard is used by EnergyStar for air purifier certifications.
EnergyStar looks at the ratio of CADR to watts on high speed. For CADR's 150 and higher this ratio needs to be at least 2.9.
In other words, if the CADR is 290 an air purifier's power consumption needs to be 100 watts or less.
In the coming years, the EnergyStar standard will be a US federal requirement to sell air purifiers in the consumer market.
While we like the CADR, in our opinion there are additional factors that should be considered when comparing air purifiers. To better understand why it helps to know how this test is performed.
EnergyStar CADR Report
The EPA EnergyStar program uses CADR as the basis for performance. They also factor in the energy usage. This results in an energy efficiency ratio which is the CADR per watt.
EnergyStar Room Air Cleaner Standard 2.0
The minimum smoke CADR to watt ratio standard.
| Smoke CADR Range | Minimum Smoke CADR/Watt |
| 30 ≤ CADR < 100 | 1.9 |
| 100 ≤ CADR < 150 | 2.4 |
| CADR ≥ 150 | 2.9 |
From the table above, this means that for a CADR at or above 150, the smoke CADR needs to be at least 2.9 times higher.
For a CADR rating of 250, this means the power on high needs to be 86 watts or less. That is 250/2.9.
To put this in perspective, a 250 smoke CADR can clean 387.5 sq ft. The formula is 250 CADR x 1.55 = recommended square foot coverage.
EnergyStar Room Air Cleaner Standard 3.0 (effective Oct 2025)
| PM2.5 CADR Range | Minimum IEF |
| 30 ≤ CADR < 100 | 4.4 |
| 100 ≤ CADR < 150 | 5.4 |
| CADR ≥ 150 | 5.6 |
Integrated Energy Factor (IEF): The energy the air purifier uses when it is in standby mode and its active top speed mode energy. This is fully defined as the measured PM2.5 CADR per watt.
How CADR is Tested
- The CADR is measured with the air purifier run on the highest fan speed. If you will not be running the air purifier on a lower fan speed then the CADR that you will realize will be lower.
- The CADR is tested with a new, clean filter so it does not reflect the performance of the air purifier over time. A small, thin filter may test well in the CADR test but soon after show a large drop in performance. To better understand this our suggestion is to find out how much filter media is in the filters. In addition the size of the air filters will factor into the expected performance over time. A large filter with a lot of filter media will perform much better than a smaller, thinner filter. You may want to watch out if the manufacturer does not provide this information.
- The CADR rating does not factor in noise level.
- The CADR is not a safety test so it does not measure ozone production, motor reliability or energy usage.
How To Choose An Air Purifier By Room Size
The key to having clean air in your home is to ensure the filters are of sufficient quality and there is proper air flow. To help you make the right choice we suggest you read our guide on air purifier room size.
What CADR rating do I need for my room?
The rule is simple: multiply your room's square footage by 2/3. That number is the minimum CADR you need to clean the air about five times per hour (4.8 air changes per hour, or ACH), which is the threshold most allergists and indoor-air-quality professionals recommend for allergy sufferers.
A few examples:
- 150 sq ft (small bedroom) → CADR ≥ 100
- 300 sq ft (master bedroom) → CADR ≥ 200
- 500 sq ft (large living room) → CADR ≥ 335
- 800 sq ft (great room) → CADR ≥ 535
- 1,200 sq ft (open-plan main floor) → CADR ≥ 800
This is the same formula AHAM publishes, the same one ENERGY STAR uses, and the same one we use to recommend specific air purifiers for allergies to specific room sizes.
CADR by room size — quick reference
| Room size | Minimum CADR (4.8 ACH) | Lower bound (2 ACH, light use) | Example use case |
|---|---|---|---|
| 100 sq ft | 67 | 28 | Walk-in closet, small office |
| 150 sq ft | 100 | 42 | Small bedroom, nursery |
| 200 sq ft | 134 | 56 | Standard bedroom |
| 300 sq ft | 200 | 84 | Master bedroom, home office |
| 400 sq ft | 268 | 112 | Living room |
| 500 sq ft | 335 | 140 | Large living room |
| 600 sq ft | 400 | 168 | Open-plan living/dining |
| 800 sq ft | 535 | 224 | Great room, finished basement |
| 1,000 sq ft | 670 | 280 | Open-plan main floor |
| 1,500 sq ft | 1,005 | 420 | Whole apartment |
For 9-foot ceilings, multiply the CADR requirement by 1.13. For 10-foot ceilings, multiply by 1.25.
Worked example: sizing a purifier for a 400 sq ft bedroom
A 400 sq ft bedroom with an 8-foot ceiling has a volume of 3,200 cubic feet. To clean the air 4.8 times per hour, the purifier needs to move 3,200 × 4.8 = 15,360 cubic feet per hour, or 256 CFM. CADR is published in CFM, so a CADR of 268 (the 2/3-of-square-footage shortcut) gives you slightly more than 4.8 ACH — exactly what you want for allergy or asthma control. For a 400 sq ft bedroom, look for an air purifier with smoke CADR of at least 240, which is what the AirMend™ 270HB (smoke CADR 237) and Mod Jr. (smoke CADR 234) deliver.
What is a good CADR rating?
"Good" depends entirely on your room. A CADR of 100 is excellent for a 150 sq ft nursery and inadequate for a 400 sq ft living room. The right way to evaluate a CADR rating is to compare it against your specific room size using the 2/3 rule above.
That said, AHAM considers any rating above 240 to be "high" and uses that threshold in some of its certifications. The CADR scale tops out at 450 — AHAM doesn't publish higher numbers, so a purifier rated 450 has been tested at or above that ceiling. Anything from 200 to 350 is the sweet spot for most home applications. Below 100, the purifier is suitable only for small enclosed spaces.
For context, here's how common ratings map to typical room recommendations:
- CADR 50–100 — small offices, closets, bathrooms
- CADR 100–200 — bedrooms, home offices, dorm rooms
- CADR 200–300 — living rooms, master bedrooms, classrooms
- CADR 300–450 — large living areas, open floor plans, small apartments
- CADR 450+ — whole-floor coverage, large open-plan spaces, commercial settings
Why CADR has three numbers: smoke, dust, and pollen
AHAM tests purifiers against three specific particle types, each representing a different size range. You'll see all three on the AHAM Verified seal:
- Smoke CADR — Particles 0.09 to 1.0 microns. The smallest of the three, and the hardest to capture. Smoke CADR is the most demanding of the three ratings; if a purifier hits its target smoke CADR for your room, it will comfortably handle dust and pollen too.
- Dust CADR — Particles 0.5 to 3.0 microns. Includes dust mite debris, fine household dust, and the carrier particles for many indoor allergens.
- Pollen CADR — Particles 5.0 to 11.0 microns. The largest of the three. Includes tree pollen, grass pollen, ragweed, and similar large airborne particles.
A well-designed HEPA purifier will have similar numbers across all three — usually within 10–20 of each other. A large gap between dust CADR and smoke CADR (where smoke is much lower) can indicate a purifier with adequate filtration but poor airflow at the speeds needed for fine-particle removal. When in doubt, size your purifier using the smoke CADR. It's the most conservative number, and it's the one we publish across our entire line for that reason.
AHAM Verified: what the seal tells you
The AHAM Verified seal means an independent laboratory has tested the purifier under standardized conditions and confirmed its published CADR ratings. AHAM (the Association of Home Appliance Manufacturers) maintains a public directory of verified products at ahamverifide.org.
What the seal verifies:
- Tested CADR for smoke, dust, and pollen under controlled laboratory conditions
- Suggested Room Size — AHAM's calculation of the maximum room size the purifier can effectively clean
- Independent testing — the test isn't run by the manufacturer
What the seal doesn't verify: filter life, noise levels, energy consumption, build quality, or warranty. Those are separate disclosures the manufacturer makes on their own. For allergy and asthma applications, where the purifier's performance is genuinely consequential, AHAM Verified is the floor, not the ceiling.
How CADR compares to CFM and ACH
CADR is often confused with two related airflow metrics. The differences matter for sizing.
CFM (cubic feet per minute) measures the total volume of air the purifier moves through itself per minute, regardless of what's in the air or how clean it comes out. A purifier's CFM is always higher than its CADR — sometimes substantially higher — because CADR is the clean air delivery rate, adjusted for the filter's actual capture efficiency. CADR is CFM × filter efficiency. Two purifiers with the same CFM can have very different CADR ratings depending on filter quality and airflow geometry.
ACH (air changes per hour) measures how many times a purifier can fully replace the air in a specific room per hour. ACH depends on both the purifier's CADR and the room's volume. For allergy control, the goal is 4.8 air changes per hour — the same threshold the 2/3 sizing rule produces. Lower ACH (2 changes per hour) is acceptable for general air quality but isn't enough for active allergy management.
Practical version: CFM is what the unit can move; CADR is what the unit can actually clean; ACH is whether that cleaning capacity is enough for your specific room.
What CADR doesn't measure (and where the spec falls short)
CADR is the most useful single number on an air purifier — but it isn't the only number that matters. Three limitations worth knowing.
CADR doesn't measure noise. Two purifiers with identical CADR can differ by 10+ dBA at the speed required to hit that rating. A purifier that's quiet on its lowest setting and unusably loud at the speed needed for its rated CADR isn't going to do the job. Always check the dB range at full speed.
CADR doesn't capture gases, VOCs, or odors. It only measures particle removal. If pet odors, cooking smells, or off-gassing chemicals are part of why you want a purifier, you need an activated carbon stage — see our TrueCarbon series for HEPA-plus-carbon options.
CADR doesn't account for ultrafine or nanoparticles. The smallest particle size in AHAM's test methodology is approximately 0.09 microns. Particles smaller than that — including some viruses and combustion ultrafines — aren't captured in the rating. HEPA media does capture them; AHAM just doesn't measure that range.
CADR is the floor for evaluating a purifier, not the ceiling. Pair it with noise specs, filter life, and (if relevant) activated carbon performance.
Frequently asked questions about CADR
What does CADR stand for?
CADR stands for Clean Air Delivery Rate. It's an industry-standard measurement, developed by AHAM (the Association of Home Appliance Manufacturers), that quantifies how much filtered air an air purifier delivers per minute. CADR is measured in cubic feet per minute (CFM) and is tested separately for smoke, dust, and pollen particles.
What is a good CADR rating?
"Good" depends on your room size. The general rule is that CADR should be at least 2/3 of your room's square footage to deliver 4.8 air changes per hour — the threshold most allergists recommend. AHAM considers any rating above 240 to be "high," and the CADR scale tops out at 450.
How do I calculate the CADR I need?
Multiply your room's square footage by 2/3. A 300 sq ft room needs CADR ≥ 200; a 600 sq ft room needs CADR ≥ 400. This gives you 4.8 air changes per hour at an 8-foot ceiling height. For taller ceilings, multiply by 1.13 (9-foot) or 1.25 (10-foot).
What's the difference between smoke, dust, and pollen CADR?
All three are tested by AHAM but cover different particle sizes. Smoke CADR (particles 0.09–1.0 microns) is the most demanding. Dust CADR (0.5–3.0 microns) covers fine household dust and dust mite debris. Pollen CADR (5.0–11.0 microns) covers the largest particles. A well-designed purifier will have similar ratings across all three.
Is CADR the same as CFM?
No. CFM measures total airflow through the purifier. CADR measures the clean air delivered, adjusted for the filter's capture efficiency. A purifier's CFM is always higher than its CADR. CADR is the more useful number for evaluating real-world cleaning performance.
What does the AHAM Verified seal mean?
AHAM Verified means an independent laboratory has tested and confirmed the purifier's CADR ratings under standardized conditions. The seal verifies tested CADR (smoke/dust/pollen) and AHAM's suggested room size. It doesn't verify filter life, noise, or energy use — those are separate disclosures. AHAM publishes the full directory at ahamverifide.org.
Does a higher CADR always mean a better air purifier?
Not necessarily. A purifier with high CADR but a noise level that's intolerable at high speed won't get used at the setting needed to deliver that CADR. CADR is the best single spec for cleaning performance, but you should pair it with noise data, filter life, and (for odors and VOCs) activated carbon specs.
Summary
The AHAM AC-1 CADR rating is a good starting point in comparing air purifiers. However, to make an informed choice we feel more information is needed.
Here is a short list of the areas we recommend you consider when buying an air purifier:
- CADR Rating
- Filters: efficiency, size and amount of filter media
- Noise level
- Motor quality
- Safety – no ozone and uses no technology that could introduce contaminants. Look for air cleaners certified by CARB (California Air Resources Board) that are mechanical to ensure no chance for ozone.
The CADR is managed by AHAM (Association of Home Appliance Manufacturers). Oransi is an AHAM member.
This article was written by Peter Mann, the founder of Oransi. He is the Chair of the AHAM Air Cleaning Council. This is the industry group who oversees the AHAM air cleaning test standards including the AC-1 particle CADR.
CADR Calculator and Model Recommender
Enter your room size to calculate the required Clean Air Delivery Rate (CADR) and get a model recommendation.
