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How to Measure Room for Air Purifier

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Updated January 14, 2022

If you’re looking to figure out how to measure your room for a high-performing air purifier, you’re in the right place. This step-by-step guide will teach you the process of finding square footage, understanding airflow rate, and more. By the end, you’ll understand how to measure each room to find the air purifier model that works best for your house.


  • Air purifiers all have different ratings which can be understood by measuring the square footage of your room.
  • Cubic Feet per Minute, or CPM, is the most commonly used measurement to figure out how much airflow the air purifier can supply.
  • Having somebody help you measure and double-check your work is highly recommended.

Tools Needed: Tape Measure, Pen or Pencil, Paper, Calculator

Measuring A Room For An Air Purifier


All of the required are household staples. First, find a measuring tape. A pen and a piece of paper are the next two components. After that, you just need a calculator. There are also online calculators available for finding square footage where you can just plug in the measurements.


Use the tape measure to find the length of two of the walls in your room. Make sure to write down measurements as you go. Once you’re done, have your helper take measurements, as well, to make sure it was done correctly. It is very important you get the measurements correct to maximize air purifier efficiency. This is because air purifiers have different ratings that are understood using the room’s measurements.


To calculate the square feet, you’ll just need to multiply the length of the room by the width. This will give you what your square footage is. Don’t worry about the ceiling heights for now.


Insider Tip

If you are new to the world of digital photography, learning how to manual focus a digital camera is an important step, despite advances in auto focus performance in both new and mirrorless systems.

Have the person helping you check your math, as well. Mistakes while finding the square feet of your room can mean getting an improperly sized air purifier. That means your air won’t be as clean as you might like it to be.

Tips for Measuring Square Feet of Your Room

Have a Friend Check Your Work

Let’s face it: most of us aren’t exactly mathematicians. Having a friend look over your work is never a bad idea. Buying an air purifier that can’t circulate air for the square feet of your room is a waste of money. Have a helper who can check your work and make sure the square feet are measured correctly.

Learn About CFM (Cubic Feet per Minute)

Simply put, CFM (Cubic Feet per Minute) is a unit for measuring airflow or the volume of air moved per minute. It’s the most commonly used way to figure out if an air purification unit is up to the task of cleaning the room it’s in. Finding CPM is easy and requires adding ceiling heights to your calculations.

Additionally, most effective air purifiers must have a HEPA filter. You need to know how you can open a HEPA air purifier so as to avoid damaging it.

Insider Tip

Manual focusing is the process of turning the focus ring on the lens by hand.


How many air purifiers do I need? One for each room?

It is recommended to have one air purifier in each room. However, there are whole-house air purifiers that take away the need to have multiple units.

Can you use multiple air purifiers in one room?

You can, but it isn’t going to clean the air any better than a single unit with the correct CADR rating. CADR (Clean Air Delivery Rate) is the industry standard for air purifiers. It’s better to get the right size air purifier than rely on multiple smaller ones.

What size air purifier is best for me?

There are several factors that come into play when deciding what type of air purifier is best for you. Do you need a portable air purifier? Is noise level important? How about the fan speed? Do you want a remote control?

STAT: Making sure your air purifier has a HEPA filter will ensure you get rid of at least 99.97% of aerosol-sized particles and smaller. (source)