What is a good cadr rating for air purifier?

Several households across the country use air purifiers to improve indoor air quality. Air purifiers filter out contaminants found in the air to provide clean and breathable air for you and your family.

Air purifiers come in various models and use different technologies to work efficiently.

There are several considerations to keep in mind while purchasing a new purifier for your household. You want to ensure that your purifier can handle the multiple different pollutants in your environment.

You also must ensure that the purifier you get works efficiently in your household and fits the size of your rooms. Indoor air quality is quickly becoming essential to maintaining good health in modern times, and as such, purchasing an air purifier that can work in your environment is vital.

There are several air purifiers in the market that claim to deliver the best results, which makes it harder to pick the right air purifier for your household. One way you can be sure of the quality of your air purifier is by looking up its CADR rating.

This is a standardized rating system provided by the Association of Home Appliance Manufacturers (AHAM). The CADR rating of an air purifier will give you a clear indication of how well the air purifier works and whether it will be effective for your household.

An independent body provides this rating with lab-tested results. Not all air purifiers on the market will have a CADR rating, but keeping this metric in mind is worthwhile.

Knowing an air purifier’s CADR rating is currently the best indication of how well an air purifier will perform in your household. 

The CADR rating system was first developed as far back as the eighties. In the past, the benchmark for air purifiers was the maximum airflow, measured in cubic feet per minute. While this gives an indication of how much air an air purifier can move, it doesn’t mention how effective a purifier is.

The CADR rating was designed to measure how effective an air purifier is at removing common pollutants such as dust, pollen, and smoke.

Tests are conducted for various sized particles under each category to provide a CADR number for each type of contaminant.

The average of these individual results provides the overall CADR rating for your air purifier. The advantage of this is you will know whether an air purifier is better at removing a certain type of pollutant.

For example, if your household has more dust than smoke, you can look for an air purifier with a higher dust CADR number even if the smoke CADR number is lower.

Comparing CADR numbers is the best metric to find an air purifier that works for your specific air cleaning needs. It is also helpful while determining an efficient air purifier for the size of your household. 

What does the acronym CADR stand for?

Clean air delivery rate.

CADR stands for clean air delivery rate. A standardized rating measures an air purifier’s cleaning effectiveness for particles ranging from 0.1 to 11 microns in size. This rating system was developed by the Association of Home Appliance Manufacturers (AHAM).

It is an independently conducted rating that is industry standard and conducted in sealed lab testing chambers. It also makes it a reliable and essential metric while comparing different air purifiers in the market.

How important is CADR rating?

Understanding CADR of air purifier

A clean air delivery rate gives the best indication of how well your air purifier will perform. Since the ratings are conducted with industry-standard testing, you can use proven numbers to make your decision instead of mere claims.

Comparing CADR ratings of different air purifiers can enable you to choose the most effective and powerful unit for your household. This rating specifies how quickly an air purifier can remove contaminants like dust, pollen, and smoke from your environment.

Air purifier models that have a higher CADR rating will be able to clean space more quickly than purifiers with lower ratings. While high CADR ratings are good, you have to make sure you get an air purifier that can efficiently clean the space you have. 

Purchasing an air purifier with a higher CADR than you need can be counterproductive and cause wastage. Purchasing an air purifier that has a CADR rating of around two-thirds of your room’s area will guarantee you clean air that is provided effectively.

For instance, a room that measures 10 feet by 30 feet has an area of 300 square feet. Two-thirds of that is 200, meaning you need an air purifier with a clean air delivery rate of at least 200 for this specific room. 

One of the drawbacks of the CADR system is that it doesn’t measure effectiveness at removing odor or gasses. It also doesn’t measure the removal of viruses, bacteria, ozone, or volatile organic components.

The CADR system doesn’t offer a reliable comparison if removing these pollutants is a primary concern. Another drawback is that CADR is measured for new purifiers operating at the highest fan speed.

Over time, your air purifier’s filter will collect more particles and reduce its efficiency, hence lowering its CADR rating.

Similarly, if you run your purifier on lower fan speeds, you can expect the CADR rating of your air purifier to drop. 

Despite these limitations, the CADR ratings of an air purifier are a critical metric to consider while purchasing a new air purifier. It will help you determine a specific model’s efficiency, size, and usability and whether it will work in your unique environment.

How do you calculate CADR for air purifier?

CADR measures the three most common contaminants found in modern households: dust, pollen, and smoke. CADR provides an overall rating and individual ratings for these three categories. This also helps you pick an air purifier for specific cleaning needs.

 The CADR ratings are based on lab testing that measures the efficiency of an air purifier in cleaning contaminant particles of different sizes.

An air purifier is typically tested in a sealed lab room that measures 1008 cubic meters for 20 minutes. The pollutants in the air are measured at each stage of testing.

The CADR number is calculated as the air purifier’s removal rate minus the natural decay rate of the air particles multiplied by the test room’s volume(1008). The formula for this is 

CADR in cfm = [rate of purifier while on-natural decay] x 1008

This means the tests are based on how much air can flow through the air purifier, measured in cubic feet per minute(cfm). For more accurate results, the tests are also based on how many particles are removed from the air, discounting particles that naturally fall to the floor.

When you know the cfm for an air purifier, you can then calculate what sized rooms the purifier will perform well in. In most cases, it is recommended to get an air purifier with a CADR rating around two-thirds the size of your room.

What is the best CADR rating air purifier?

One of the best CADR rating air purifiers currently in the market is the Medify MA-50 Air Purifier with H13 True HEPA Filter. It has the highest CADR rating of 500 cubic meter/hr , and includes a touch operation panel with 2-12 hour timer, 4 fan speeds, sleep mode, filter replacement indicator, and child lock, which is great for both kids and pets. This makes it one of the more efficient models with a high CADR rating and efficiently provides clean indoor air.

The other four top performing air purifiers with high CADR ratings are:

MOOKA Air Purifier for Large Rooms True HEPA Air Filter with 300 m³/h CADR.

LEVOIT Air Purifier for Home Large Bedroom with CADR of 240 m³/h.

Germ Guardian 4 in 1 Air Purifier With True HEPA Filter: CADR: Smoke 235 dust 239 pollen 237

Coway Air Purifier: CADR: Dust 246 / Pollen 240 / Smoke 233 cb. ft.

FAQ Section

1. How do you convert CADR to cfm?

This depends on how your CADR rating is measured. You can convert cubic meters per hour into cubic feet per hour by multiplying the value by 35.3147. You can then divide the value of cubic feet per hour by 60 to get the value of cubic feet per minute(cfm).

 Another more straightforward calculation is multiplying the CADR rating in meters per hour by 0.588 to get the CADR in cubic feet per minute.

2. How do you calculate ACH from CADR?

Knowing the cfm will allow you to calculate air changes per hour(ACH). Multiplying cfm by 60 will give you the air moved per hour value. It will enable you to determine how long the air purifier will take to clean the air in your room.

Your ACH rating is then calculated by dividing the cubic feet of air moved per hour by the cubic feet volume of your room. For example, if your air purifier has a CADR rating of 200 cfm, multiplying by 60 will give you 12000 cubic feet per hour of air moved.

If your room measures 20 feet by 30 feet with walls that are 10 feet high, you should multiply the length by width by height to get the total volume.

In this case, your room measures 6000 cubic feet. Dividing air moved by room volume is 12000 by 6000, giving you 2 ACH. This lets you know that the air in your room will change twice per hour.

It may not be enough for this particular room as it is recommended to have a purifier of at least 4 ACH. This means that an air purifier of 400 cfm will better suit your needs.

3. What is a good CADR rating for smoke?

Smoke behaves differently from other contaminant particles. Smoke particles tend to be smaller and don’t have high natural decay rates.

Air purifiers come with different CADR ratings for each type of particle. A purifier that has a high dust CADR rating may not have a high smoke CADR rating.

CADR ratings on air purifiers are usually the averages of the ratings for dust, pollen, and smoke. To know what a good CADR rating for smoke for your household is, you should know the individual smoke CADR rating for the specific purifier you are considering.

As with other CADR ratings, you have to ensure that your smoke CADR rating is around two-thirds the size of your room. For example, if your room measures 600 hundred square feet, you need a purifier with a CADR smoke rating of 400, which is two-thirds of 600.

4. What is the CADR of Dyson air purifier?

Dyson air purifier

Dyson lists their CADR as 70, which is relatively low for an air purifier. The higher the clean air delivery rate, the more effective it is.

Comparatively, other high-end air purifiers perform better than Dyson air purifiers.

5. How long does it take an air purifier to clean the air in a room?

How long an air purifier takes to clean air in a room depends on two factors. How large the room is, and how effective the purifier is. Due to the variable factors, an air purifier can clean a small room in as little as half an hour and take a couple of hours or more for a large room.

To know precisely how long a specific air purifier will take to clean a room in your household, you can calculate the air changes per hour or ACH to know how many times the air in your room is cleaned per hour. Dividing 60 by your ACH rating will let you know how many minutes it takes for your air purifier to clean your room once.

Since contaminants are always present, your air purifier should be turned on all the time. Even though an efficient air purifier can clean the air in a room once in less than an hour, it is essential to leave it on so it can continue to clean the air that flows through your room. 

6. What do doctors say about air purifiers?

Poor indoor air quality leads to many health issues, especially in those suffering from asthma or pollen allergies. The longer air quality is left unchecked, the more chances of developing long-term respiratory problems.

This is especially true in the urban areas where air quality worsens due to pollution and other factors. Clean and high-quality indoor air can alleviate these problems and ensure long-lasting respiratory health.

As such, air purifiers are recommended by doctors for use in typical households. Clean air offers several health benefits that can’t be ignored.

7. Are air purifiers safe?

Air purifiers were thought to be unsafe due to a few problematic air purifier models. These models have given air purifiers a bad reputation due to the permanent damage they have caused to health. Not all air purifiers are dangerous.

Only air purifiers that release ozone as a byproduct are dangerous and should be avoided at all costs. Ozone can cause permanent damage to health with even the slightest exposure. As long as you don’t use an ozone-generating air purifier, they are safe and healthy to use.

Choosing a HEPA air purifier is guaranteed to improve your health. Doctors recommend getting an air purifier for your household as long as it doesn’t generate ozone.


Air quality is constantly getting worse, especially in urban environments. Air purifiers offer a solution by removing pollutants in the air to provide clean and fresh indoor air.

Using an air purifier with the required CADR in your home can benefit you and your family if you pick the right one. The air purifier market is saturated with several makes and models that rely on different technology and work differently.

As homeowners, it can be a little challenging to pick an air purifier model that is right for your household. Getting the wrong air purifier can be ineffective and, in the worst case, even cause more damage than benefits.

Luckily, air purifier manufacturers use a standardized rating system that can help you determine whether an air purifier is right for you. The CADR rating system can inform you about the effectiveness of your new air purifier. It shows proven and reliable results that determine how good an air purifier is at removing the most common types of contaminants found in the air.

In addition, you can choose a model that will work best for the size of your home by knowing its CADR rating. While not all air purifiers have a CADR rating, it is an important metric that shouldn’t be ignored.

This guide aims to discuss the merits of the CADR rating system and how it can be beneficial in determining whether an air purifier is right for your household.

Hopefully, you can use this knowledge to make a more confident and informed decision about purchasing a new air purifier.


About The Author

Olivia — a self-confessed air quality addict — is a home climate enthusiast, fresh air advocate, and someone with deep personal experience and knowledge about mold extermination. Her work was mentioned in countless notable humidity publications. Previously she was an editor at Mold Remediation.