What Is a Good CADR Rating for an Air Purifier? Here’s the Real Deal

You’ve probably seen it before—some mysterious number printed boldly on an air purifier box labeled “CADR.” Most people skip over it or assume higher is better without really understanding what it means. But here’s the thing: if you care about clean, breathable air in your home, CADR is one of the few numbers you should pay attention to.

Not just because it’s technical. Because it tells you how fast and effectively a purifier can clean your air—not just run quietly or look nice. Whether you’re dealing with pet dander, wildfire smoke, or seasonal allergies, understanding CADR can help you avoid buying a machine that underperforms in your actual space.

So, let’s break it down in the clearest, most practical way possible—no jargon, no fluff.

What Is CADR in Air Purifiers and Why Does It Matter?

CADR stands for Clean Air Delivery Rate. It was developed by the Association of Home Appliance Manufacturers (AHAM) to give buyers a standardized way to compare air purifiers based on actual performance—not marketing hype.

To put it simply, CADR tells you how much clean air (in cubic feet) a purifier delivers per minute. That’s not just about having a strong filter—it also reflects how fast the unit pulls air in, filters it, and pushes it back out into your room.

Let’s say you’re using a purifier in a 200 sq. ft. bedroom. If the CADR is only 100 CFM (cubic feet per minute), that means it’s only replacing half the air every minute with filtered air. It’ll still help, but slowly—and maybe not fast enough to keep up with pollen, smoke, or pet odors. A CADR of 130–150 would be much more effective for that space.

The key takeaway? CADR is the speed and power behind the purifier. Without it, even the best filters won’t make much difference if the airflow is weak.

How CADR Ratings Work: Dust, Smoke, and Pollen

When you look at CADR ratings, you’ll usually see three separate numbers, each representing a specific type of particle:

• Dust CADR: For medium-sized particles like lint, pet dander, and household dust.

• Pollen CADR: For larger particles like plant pollen and mold spores.

• Smoke CADR: For the smallest particles, including tobacco smoke, wildfire smoke, and VOCs (gaseous pollutants).

Each of these is tested separately in a lab using a sealed room setup. A purifier is turned on, and researchers track how fast it removes each type of particle.

Here’s why that matters: not all purifiers are equally effective at all three types. Some may have a very strong dust CADR but a weaker smoke CADR, which could be a dealbreaker if you’re living in wildfire-prone areas or dealing with chemical fumes from nearby traffic.

👉 Example: If a purifier has a smoke CADR of 90, but you’re trying to clear out cigarette smoke in a 300 sq. ft. room, it simply won’t do the job well. You’ll still smell it and feel it. In that case, you’d want a smoke CADR of at least 200 to feel a noticeable improvement.

Also, some purifiers focus too much on airflow and not enough on filter quality. So even if the fan is strong, without a good filter like a HEPA or activated carbon layer, it might just be pushing unfiltered air around. That’s why CADR works best when combined with a quality filtration system.

What Is Considered a Good CADR Rating?

Here’s where people usually get stuck. You might see a purifier labeled for “rooms up to 500 sq ft,” but the CADR is only 150. That sounds like a good number… until you do the math.

Here’s the rule of thumb:

A good CADR should be at least two-thirds (⅔) of your room’s square footage.

Let’s say your living room is 360 square feet.

So, to clean that space efficiently, you want a purifier with a CADR of at least 240 for smoke, dust, and/or pollen—depending on your concern.

If the CADR is lower, the purifier will struggle to keep up. You’ll still breathe in allergens, odors will linger, and air circulation will be sluggish. On the other hand, a higher CADR means faster air changes per hour (ACH)—which is exactly what you want if you suffer from asthma, allergies, or smoke sensitivity.

Here’s a quick cheat sheet:

Tip: Don’t aim for the bare minimum. If you’re in a dusty environment, have pets, or live near traffic, aim for 10–20% above the minimum CADR. You’ll notice a real difference in freshness and relief.

How to Calculate the Right CADR for Your Room

You don’t need to be a math wizard. Use this simple formula:

Let’s walk through it:

If your bedroom is 12 ft × 15 ft, that’s 180 square feet. Multiply it:

So, a CADR of 120 or higher is a good baseline. But if that bedroom also has carpet, pets, or sits near a road, look for 150+ to stay ahead of pollutants.

For larger areas like open-plan living rooms, go higher still. You might need a CADR of 300–350 or consider using two purifiers in separate corners to cover the space more evenly.

Also, if you or someone in your home suffers from allergies or asthma, consider targeting 4–5 air changes per hour (ACH). That usually means going above the basic CADR calculation. You want the air turned over quickly and consistently.

Real-life scenario: During harmattan season or wildfire events, people often complain that their purifier “isn’t working”—when in reality, the CADR is just too low for how fast particles are entering the room. A quick upgrade to a higher CADR model usually clears the air within 20–30 minutes.

CADR and Air Purifier Efficiency: Does It Affect Performance?

Yes, CADR makes a huge difference in how well your air purifier performs. Think of CADR as the balance between airflow power and filtration effectiveness.

Even if a purifier uses a True HEPA filter, which can theoretically capture 99.97% of particles as small as 0.3 microns, it doesn’t help much if the unit can’t move enough air through that filter. That’s like having a top-of-the-line coffee filter but only dripping in one drop at a time—it’s clean, but way too slow.

CADR measures the real-world outcome: how much cleaned air it delivers each minute. So if your purifier has a low CADR, it’s not “bad”—but it might be too slow to keep your air clean consistently.

A purifier with a CADR of 100 in a large 400 sq. ft. space may struggle all day long to remove pollutants. But another unit with CADR 300 in that same space could clear the air multiple times per hour. That means:

• Less sneezing and coughing

• Fewer lingering smells

• Better sleep

• More noticeable air freshness

Also worth noting: a higher CADR doesn’t always mean more noise. Many modern models are engineered to run quietly even with strong airflow. Some allow you to set a high speed for quick cleaning, then switch to sleep mode for quiet nighttime use.

If you’re dealing with:

• Allergies → Focus on high pollen CADR

• Dusty environments → Prioritize dust CADR

• Cigarette smoke or VOCs → Look for high smoke CADR (ideally 250+)

Common Questions About CADR Ratings Answered

Let’s quickly address some of the most common and confusing questions you might still be asking.

What CADR do I need for 300 sq. ft.?

You’ll want a CADR of at least 200. This ensures your air gets refreshed fast enough to trap incoming pollutants before they build up. If the area has high ceilings or heavy pollutants, go for 250+.

Is a CADR of 250 considered good?

Yes. It’s a strong number, especially for smoke or dust. That could cover up to 375 sq. ft. efficiently and is powerful enough for most average-sized rooms.

Does a higher CADR mean better air quality?

It means faster and more consistent air cleaning. That directly contributes to better air quality, especially in areas with ongoing exposure to smoke, pets, pollen, or chemical fumes. It doesn’t mean the filters are better—it means the unit is cleaning more air per minute.

Can a purifier have too much CADR for a small room?

Technically, yes—but it’s not a bad thing. A unit rated for 500 sq. ft. will clean a 200 sq. ft. room very quickly and then slow down or maintain. Just make sure the noise level on lower speeds won’t bother you.

Why are some purifiers advertised for large rooms but have low CADR?

That’s marketing. Some brands exaggerate coverage claims using maximum airflow without accounting for filtration. Always check for the AHAM Verified seal or actual CADR ratings rather than trusting the square footage claim alone.

AHAM Verified Seal and CADR Testing Standards

The Association of Home Appliance Manufacturers (AHAM) is the independent body responsible for testing and verifying CADR ratings in a controlled lab setting.

If you see a purifier with an AHAM Verified label, that means its CADR numbers have been independently confirmed, not just created by the manufacturer. This is especially important if you’re shopping online, where it’s easy for brands to overpromise.

In AHAM’s testing:

• A sealed room is filled with controlled levels of smoke, dust, or pollen.

• The purifier is turned on, and sensors track how quickly each type of particle is removed.

• Results are used to determine the CADR score for each category.

Bottom line: Look for the AHAM Verified seal. It’s one of the only ways to know that the purifier’s claims about performance are real and not just marketing.

How to Choose the Best Air Purifier Based on CADR

When comparing air purifiers, it’s easy to get overwhelmed by features—Wi-Fi, timers, filters, modes, displays. But start with CADR, then worry about the rest.

Here’s a smart way to compare:

✅ Know your room size (in square feet)
✅ Multiply by 0.67 to get your target CADR
✅ Prioritize the pollutant that matters most to you
✅ Check if it’s AHAM Verified
✅ Compare CADR to price—is it worth the performance?

Real-world examples:

• If you live with pets: Choose a purifier with a dust CADR of 250+

• If you live in wildfire zones: Look for smoke CADR 300+

• If you suffer from hay fever: Go for pollen CADR 300+

• For open-plan homes: Consider a dual purifier setup or a whole-home solution

Pro tip: Sometimes, two smaller purifiers with 150–200 CADR each can clean large spaces more effectively than one oversized unit—especially if placed at opposite ends of the room.

Final Thoughts: Picking the Right CADR for Cleaner, Healthier Air

You don’t have to become an engineer to breathe clean air at home. But knowing your CADR numbers? That’s smart. It’s the difference between guessing and knowing your purifier is doing what you bought it for.

To recap:

• CADR = clean air delivered per minute

• Match CADR to your room size (sq. ft. × 0.67)

• Check ratings for smoke, dust, and pollen, not just one

• Prioritize units with AHAM Verified seals

• Aim for a higher CADR if you want faster, more complete air cleaning

Now that you know this, go back and re-check the purifier you were eyeing. If the CADR isn’t listed? That’s your first red flag. Look for brands that respect your right to real, measurable data—and not just buzzwords.

And remember: a purifier is an investment. Not just in clean air—but in better sleep, fewer sick days, and a healthier daily life.