CADR Rating Explained
CADR, the Clean Air Delivery Rate, is a metric 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 effectiveness in removing different particle sizes, three types of particles are tested: smoke, pollen and dust. These represent small, medium and large sized particles, and each is assigned its 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.
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 (primary 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 | Primary 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.
CADR Calculator and Model Recommender
Enter your room size to calculate the required Clean Air Delivery Rate (CADR) and get a model recommendation.
Oransi CADR ratings by model
Every Oransi HEPA model is AHAM Verified. We publish smoke CADR across the line because it is the most demanding of the three ratings. An air purifier that hits its smoke CADR target will comfortably handle dust and pollen in the same room.
| Model | Smoke CADR (CFM) | Room coverage at 4.8 ACH | Typical use |
|---|---|---|---|
| AirMend™ 150HB | 189 | 293 sq ft | Small bedroom, nursery, home office |
| AirMend™ 200HB | 208 | 322 sq ft | Standard bedroom, dining room |
| Mod Jr. | 234 | 363 sq ft | Large bedroom, living room |
| AirMend™ 270HB | 237 | 367 sq ft | Living room, finished basement |
| Mod+ | 363 | 563 sq ft | Great room, open-plan main floor |
The AirMend™ series is designed, engineered and assembled in Radford, Virginia. Full lab results and noise figures are published on each product page.
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 published 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 on both air flow and filter efficiency at once. In other words, it provides a way to compare performance across products consistently.
CADR is essentially air flow (CFM) multiplied by the efficiency of the air filter. If a purifier moves 200 CFM at 100% efficiency, the CADR is 200. At 200 CFM and 75% efficiency, the CADR is 150.
CADR is also a good way to keep from being misled by marketing claims. If a filter has very high efficiency but low air flow, CADR balances the two.
We see this commonly from manufacturers who use particle counters to demonstrate high efficiency when selling to customers. That demonstration is compelling, the shopper watches particles disappear and the test itself is valid. But it ignores air flow and noise level, so it does not give a complete picture of how the purifier will perform in a real room.
Air filtering standard
CADR is the standard in the US and is shown in CFM (cubic feet per minute). In Asia, CADR is expressed in cubic meters per hour (m³/h).
Most air purifier brands show performance in CFM, but some show m³/h in North America, which is misleading because the number looks inflated. For example, 235 CFM = 400 m³/h.
The AHAM CADR standard is also used by ENERGY STAR for air purifier certifications. ENERGY STAR looks at the ratio of CADR to watts on high speed. For CADRs of 150 and higher, that ratio needs to be at least 2.9, so a purifier with a CADR of 290 needs to draw 100 watts or less.
In the coming years, the ENERGY STAR standard is expected to become a US federal requirement to sell air purifiers in the consumer market.
While we value CADR, in our view there are additional factors worth considering when comparing air purifiers. Understanding how the test is performed explains why.
ENERGY STAR CADR report
The EPA ENERGY STAR program uses CADR as the basis for performance and factors in energy usage, producing an energy efficiency ratio expressed as CADR per watt.
ENERGY STAR 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 |
For a CADR at or above 150, the smoke CADR needs to be at least 2.9 times the wattage. For a CADR rating of 250, power on high must be 86 watts or less (250 ÷ 2.9).
To put that in perspective, a 250 smoke CADR covers 387.5 sq ft. The formula is CADR × 1.55 = recommended square foot coverage.
ENERGY STAR 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) accounts for both the energy the purifier uses in standby mode and its active top-speed energy. It is defined as the measured PM2.5 CADR per watt.
How CADR is tested
- CADR is measured with the air purifier running at its highest fan speed. If you run it on a lower speed, the CADR you actually get will be lower.
- CADR is tested with a new, clean filter, so it does not reflect performance over time. A small, thin filter may test well and then drop off sharply. Ask how much filter media is in the filter. A large filter with more media will hold performance far better than a thin one. Be cautious if the manufacturer does not publish this.
- CADR does not factor in noise level.
- CADR is not a safety test. It does not measure ozone production, motor reliability or energy usage.
For more on matching a purifier to your space, see our guide to air purifier room size.
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 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, primary 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 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. An air 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 heavy-duty 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.
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). Or use the calculator above.
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.
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. For odor removal there is a standard called AC-4 and that should be referenced as opposed to the AC-1 particle CADR.
What CADR do I need for a 500 sq ft room?
At least 335. That delivers 4.8 air changes per hour at an 8-foot ceiling. The Mod+ (smoke CADR 363) covers 563 sq ft and is the single-unit choice for that space.
Can one air purifier cover a whole house?
Generally no. CADR is measured in a single sealed room, and air does not circulate freely between closed rooms. For whole-home coverage, size a unit per room using the 2/3 rule, or prioritize the rooms where you spend the most time — typically the bedroom first.
Summary
The AHAM AC-1 CADR rating is a good starting point for comparing air purifiers. To make a genuinely informed choice, though, more information is needed.
Here is a short list of what we recommend you consider when buying an air purifier:
- CADR rating, sized to your room
- Filters: efficiency, size and amount of filter media
- Noise level at the speed you'll actually run it
- Motor quality: the most expensive and most failure-prone component
- Safety: no ozone, and no technology that could introduce contaminants. Look for mechanical air cleaners certified by CARB (California Air Resources Board) to ensure there is no chance of ozone.
CADR is managed by AHAM (Association of Home Appliance Manufacturers). Oransi is an AHAM member, and this article was written by Peter Mann, founder of Oransi and Chair of the AHAM Air Cleaning Council — the industry group that oversees the AHAM air cleaning test standards, including the AC-1 particle CADR.
