HomeZene Logo

How To Choose The Right Size Air Purifier 

Updated by

Right size plays an important role in achieving the best out of an air purifier. Because if you choose a smaller size, then it may not be efficient clearing the pollutants. And if you opt for a large option than required, then it consumes more power, resulting in higher electricity bills.

This ultimate guide on air purifier size is the answer to your question. This article has everything you need to know about choosing the right size for your room.

This write-up will help you clear the air and make you enjoy better indoor air quality. Keep reading till the end.

Let us start our discussion with air purifier types.

What are the Types of Air Purifiers?

Air purifiers usually come in four different sizes. Each type is suitable for a room of a specified size that has its measurements in square feet. They are:

  1. Small air purifier
  2. Medium air purifier
  3. Large air purifier
  4. Whole-house air purifier

Let us take a look at the room sizes each air purifier type is suitable for:

S. No Air Purifier Type Suitable For Room Size
1. Small Air Purifier A small air purifier is ideal for small rooms and personal spaces measuring up to 200 sq. ft.
2. Medium Air Purifier A medium air purifier is the best option for rooms measuring from 200 to 400 sq. ft.
3. Large Air Purifier A large air purifier is most suitable for rooms measuring between 500 and 1500 sq. ft.
4. Whole-house Air Purifier A whole-house air purifier is an ideal option for purifying the air in every room of the house.

Let us move on to choosing the right size of air purifier for your room.

How to Choose an Air Purifier of Right Size for the Room?

We know the different types of air purifiers available and what room sizes they are ideal for. As a first step, we need to measure the size of the room if we want to select an air purifier of the right size for it. So, start the process by measuring the square footage of your room that you intend to purify.

After you get the exact measurements of your room, you can choose from the four different types of air purifiers.

Picking the right type suitable for your room size helps clean the air effectively. Furthermore, it provides a respite from breathing unclean air.

Here is a step-by-step process in choosing the right size of air purifier for your room:

Step 1: Determining the Location For Placing Your Air Purifier

The first and most crucial step in choosing an air purifier of the right size is this – You need to decide the spot for placing the device. Determine the location first.

It could be a single room or many rooms, or even the entire house. You need to first decide where you intend to place the air purifier and which room you are planning to purify.

Once you have complete clarity on the above, you can easily narrow down your choice. Furthermore, it will be even more easier to compare various products and purchase the best product suitable for your application.

Step 2: Measuring the Size Of the Room in Square Footage

Here is the second step. After you decide which room you want to purify, you will have to measure its size in square feet.

Let us see how to get the measurements.

a) Measuring the square footage for a single room can be easily done. 

All you need to do is take a measuring tape and start taking the measurements.

But make sure that choose any two perpendicular walls of the room for measuring. This will help you calculate the room size in square footage.

Let us assume the length and breadth are 10 feet and 12 feet, respectively.

Then the size of the room is 10 feet x 12 feet = 20 sq. ft.

This is the measurement for a single room.

b) Similarly, if you want to calculate the size of multiple connected rooms where you intend to place the air purifier, this is what you should do.

Firstly, measure the length and breadth of each room individually.

Now, add the totals of all rooms to get the final measurement.

Let us say you have two adjoining rooms whose sizes are 120 sq. ft. and 80 ft., respectively.

Then the total square footage is 120 sq. ft. + 80 sq. ft. = 200 sq. ft.

This is the total measurement for multiple rooms.

Step 3: Comparing the Square Feet Rating Given on the Air Purifier with the Sq. Ft. Rating of Your Room

The third and final step in the process is to match the specifications of the air purifier to the room size.

We all know that the air purifier models, irrespective of size and shape, come with a square footage rating specified.

That said, each model is effective or suitable for a room of a specific size.

The ideal air purifier size is the one that fits your requirements. That means its specifications should meet the square footage of the room you want to place it in. If not exactly, it can even slightly exceed the measurements.

All you need to do is, compare the square feet rating to get the closest match for your room.

Once you get the exact size, you will be to enjoy the benefits of air purifiers to the fullest.

What are CADR And ACH?

Most air purifiers come with a CADR and ACH rating. These ratings are nothing but the figures that indicate the efficiency levels of the air purifier in purifying and removing the contaminants from the air.

If you want to get the air purification results for your room, here is an easy way to do it. All you have to do is follow the simple formula:

CADR x 1.55 = Square footage of your room.

Following this formula will not only help you determine the right size of your room but will also give the fastest air purification results.

Every air purifying unit has 3 CADR values and they are the smoke, pollen, and dust. In most cases, these values are the same for all devices.

If the values are not the same for the air purifier, do not fret. Just pick the unit with a small CADR rating and the most accurate values. You may ask how effective an air purifying device with a low CADR rating will be. You do not have to worry that such a unit will not, and it cannot purify a large room. It can, and it will do. But the only thing is that it will take more time to do it.

Let us move on to the ACH rating.

ACH is nothing but an abbreviation for air changes per hour. This is yet another crucial rating you need to look for before choosing an air purifier. The significance of this rating is that it tells you the number of times the unit can filter the air in the room per hour.

Make sure you do not buy an air-purifying device having less than a 2x ACH rating. This is not recommended. It is as good as not having an air purifier.

The best possible solution is opting for a unit with an ACH rating of more than 2x. If you are an asthma patient, we recommend you to consider one with an ACH rating of 4x.

Choosing an air purifier with the above ratings is very crucial for people who are susceptible to pollen or air pollution.

Let us say your room does not have any such outside factors or is an ideal room. Additionally, let us assume that there are no inhabitants with any respiratory problems. In such cases, choosing the right size of an air purifier is as easy as a pie. All you need to do is follow the instructions mentioned in the user manual.

Where Should You Install the Air Purifier in Your Room?

After choosing the right size air purifier, the next thing you ought to do is to install it. But, where do you install it? What is the correct position for installing it? Here is the answer. If you want to enjoy the best air purifying results in your room, the correct place of installation is in the middle of the room. 

Installing your air purifier in the middle of your room will increase the chances of filtering air faster in the room. This does not mean that if you place the unit in the corner of the room, it will not filter. It will. However, the time taken to purify all the air in the room is more than usual. The device will slowly filter the air in the whole room.

Here are a few common mistakes that many people tend to make. They either place the air purifier in a corner or just hide it behind a couch. This is completely acceptable, provided your air purifiers allow such installations. These units come specifically designed to intake air from all sides, including the top. In such cases, you will have no problem installing them anywhere.

There are many air purifying units in the market that intake air and allow outflow of air from the back. If you are using such a unit, make sure you do not install it against the wall. By doing so, you are limiting the filtration capabilities of the air purifier. Even though your device does not circulate air from the back, placing it against the wall or behind the couch is simply not a good idea. Most of the air purifiers available in the market are very powerful. They get hotter when operating. When you place such devices near any obstacle, you are reducing the lifespan of the purifier.

Hence, the ideal location for placing your air purifier should be in the middle of the room. Additionally, you need to place them on an elevated surface like a table for better access to the air circulation. If it is not possible to do it, try placing it somewhere close to the middle of the room. Avoid installing them on the walls, behind couches, etc.

Can an Air Purifier Become Too Small or Big for Your Room?

Technically, an air purifier can be too big for a room. However, it will still clean the air efficiently. The only downside is that you will have to pay more for the purifying unit. Additionally, you will have to incur maintenance costs by changing the costly filters regularly.

If you are planning to buy an air purifying unit for a smaller room, you will have to buy one accordingly. Purchasing a device with a cleaning capacity of 3,500 square feet will not make any sense. It will be too powerful for your room. Besides that, it will cost you too much to purchase, consumes more electricity, and also requires expensive and quality filters.

Hence, the best option is to choose an air purifier that perfectly fits your room size. It is advisable to look for the square footage rating indicated on the unit before you purchase one.

For example, let us assume that the size of your room is about 150 sq. ft. In such a case, look for an air purifier unit having a square footage rating equal to the room measurements or slightly more than it.

You can even go with an air purifier with a square foot rating of 200 or 250. This rating is equally efficient as a unit having 150 square feet rating suitable for a space of this size.

Can I Use Multiple Air Purifiers in One Room?

Yes, you can always use multiple air purifiers in one room. All these units work together to purify the air in the room. This is, however, a suitable option for a larger room.

Let us say the size of your room is around 1,200 square feet. You can use two air purifiers in the same room with a capacity of purifying air up to 600 square feet. This will help in cleaning the air in the room effectively.

Similarly, you could even use three smaller air purifying units with a capacity of up to 400 square feet each.

How Many Air Purifiers Do I Need?

The total number of air purifiers you need in your home is entirely dependent on you. We advise having one air purifier each for a room where you mostly spend your time.

Let us say you spend most of your time in your bedroom, living room, and your office room. In such a scenario, you require three units for each room.

You may say that you hang out mostly in the bedroom and living room. If such is the case, it is ideal to have two air purifiers.


To conclude, choosing an air purifier of the right size helps you enjoy the benefits to the maximum. If you do not know how to select the air purifier size, this article should help you a great deal. Follow the steps highlighted in this article to get a unit of the appropriate size. Let us know in the comments if you feel this write-up answered all your questions and provided you with all the information you need.

Do not hesitate to write to us if you still have any queries on air purifier size or need more information. We would try our best to clear all your doubts at the earliest.

Share your feedback with us by letting us know if we have missed out on any points. Please feel free to add your inputs to this article. We welcome your suggestions and would love to hear from you.

Stay healthy and stay safe!!!

Related Posts:

Leave a Reply

Your email address will not be published.