Just like most of the home appliances out there, air purifiers come in different sizes.

That means you can not just pick one up and expect it to work flawlessly for your room. So, having a fair idea regarding the air purifier room size calculator is a must.

To calculate the right air purifier for your room, you need to consider the size of your room and the air changes per hour.

The CADR (Clean Air Delivery Rate) rating also comes into play for selecting the perfect size of air purifier for your home.

However, without knowing how to use that data, you can not end up with a number.

And even if you end up with a number, it might not make sense. But do not worry; we are here to make things easier.

## Things that You Need to Know About the Air Purifier Calculator

Before finding out what size air purifier you need, there are two primary resources, you should know. Let’s talk about them before we get deeper into the process –

### Air Purifier Room Size Calculator

This depends on the CADR rating. The input size of the space, which is the ceiling height + square footage of the room, and ACH (Air Changer Per Hour).

These factors will let you calculate the required size of the air purifier. Also, you will get the right CFM (Cubic Feet Per Minute) CADR rating for the room.

### Air Purifier Size Chart

It is a complete chart of the size of the air conditioner you need for the rooms. This chart has all the data you need for a room between 100 square feet and 2000 square feet.

And the ACH rating in this chart will be between 2 ACH and 5 ACH.

For example, the chart will tell you that you are going to need an 80 CFM air purifier for a 300 square feet room with 2 ACH.

And at 5 ACH, you will need an air purifier that has 200 CFM.

## What Determines the Size of the Air Purifier?

When it comes to choosing the right size for the air purifier, you need to consider the following two factors –

### Size of the Room

This factor will have the highest overall impact on the size of the air purifier.

However, you are not looking for the square footage of the room. Instead, you should be interested in the amount of air that the room can fit in.

So, you will need to put the ceiling height in the equation.

By putting that in, you will end up with the volume of air that the room can fit. And this measurement is a must for calculating the size of the air purifier.

### Air Changes Per Hour

ACH, or Air Changes Per Hour, states how big the air purifier needs to be to change the room for a particular amount of time in one hour.

At a minimum, you need an air purifier that can change your room’s air twice an hour. That is, you need 2 ACH.

However, if you are allergy-prone, you would want to increase the ACH to 5. That means the air needs to be changed once every 12 minutes.

## How to Size an Air Purifier for Your Home?

After knowing how much air your room can fit and how many times you want the air to change in an hour, you need to use them to determine the size.

Let us give you an example of how you need to carry out the calculation –

### The Calculation for Determining the Size of the Required Air Purifier

Consider that you have a room that is 400 square feet in size. And the ceiling height is 7 feet.

So, the air volume inside the room would be 400 square feet x 7 feet = 2800 cubic feet.

Now, if you want to get an air purifier that changes the air 2 times per hour, multiply 2800 by 2. You will end up with 5600 cubic feet.

So, for a room with 400 square feet and 7 feet ceiling, you would want an air purifier capable of providing 5600 cubic feet of purified air.

That is if you consider 2 ACH.

## The Size of the Air Purifier and CADR Rating

After the calculation process that we have described above, you will end up with a number that will be in cubic feet.

So, **how do you compare it with the air purifier’s CFM rating?**

Consider an air purifier with a 300 CFM rating. It will provide 300 cubic feet of air in one minute.

You will need to convert it into cubic feet per hour. That is, you should multiply it by 60.

So, a 300 CFM air purifier can offer 18000 cubic feet of air per hour.

That air purifier will be too big for a 400 square feet room with a target of 2 ACH.

However, it might be a perfect pick if you want to increase the ACH.

## How Do You Measure a Room for Air Purifier?

In case you got yourself lost in the calculation discussion that we had above, here are the steps that you need to go through for the calculation in a step by step process-

- Take the measurement of the length of the room that you want the air purifier to be.
- Measure the width of the room.
- Note down the height of the ceiling.
- Multiply all the three numbers that you have just collected, which are length x width x height. You should end up with cubic feet. This is the volume of air that your targeted room can hold.
- Decide how many ACHs you want. If you are allergy-prone, choose ACH 5. In the other cases, choose 2.
- Multiply the ACH by the number that you got in step four. That is, the length x width x height x ACH. The number that you will end up with is the amount of air that you want the room to have per hour.
- For ease of choosing the air purifier, divide the number by 60. After that, you will have a number that will state the CFM rating you need to look for in air purifiers.

In simpler words, the equation that you are working with here is (length x width x height x ACH) / 60.

So, for more simplicity, the equation is (Area x height x ACH) / 60. Now, let us give you an example to make things easier.

If you have a room that is 900 square feet in size and it has an 8 feet high ceiling, the calculations will be something like this –

(900 x 8 x 2 ACH) / 60 = 240.

This 240 is the CFM rating of the air purifier that you would want for that particular room.

But if you are allergy-prone, put 5 on the ACH number, which will make you end up with 600 CFM.

## What to Do If You Have High CFM Requirement?

It might be hard for you to obtain air purifiers with high CFM ratings.

Generally, the air purifiers will hover around 200 CFM ratings.

So, what do you do when you need a high CFM for your room? Well, you can combine multiple air purifiers.

For example, if you need 400 CFM, you can just combine two 200 CFM air purifiers.

When you run them together, you will meet the targeted CFM rating.

**See More**: Why is my Alen air purifier beeping?

## Frequently Asked Questions

### 1. Can I use an air purifier in a small room?

You can use an air purifier in a small room. However, in such cases, it would be better to get air purifiers that have a relatively lower CFM rating. Otherwise, you will just be wasting energy, as the large air purifiers will be overkill for small-sized rooms.

### 2. How much space does an air purifier need?

To make the air purifiers work optimally, you will need around 18 inches of clearance from all angles. That means the air purifier needs to be 18 inches away from all the walls or obstructions.

### 3. Will an air purifier work if the room is too big?

A small-sized air purifier will not correctly purify the indoor air if the room is too big. For large-sized air purifiers, you need to pick large-sized air purifiers that have relatively high CFM ratings.

## Final Words

So, for the air purifier room size calculator, you need to consider three specific things.

Firstly, you should take note of the area of the room. Secondly, the height of the room. And finally, the ACH, which is Air Changes per Hour.

Multiply all that and divide by 60 to get the required CFM rating that you have to target.

Last Updated on December 1, 2022