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What Size Dehumidifier Do I Need?

Last updated April 21, 2023

Danny as been writing about air purifiers for 10+ years. He is a major fan of home technology, which makes him the perfect person to test and evaluate products for HouseFresh

Our verdict:

Dehumidifiers come in many shapes and sizes. To most accurately and efficiently remove the humidity from your space, you’ll need to do a bit of groundwork to ensure you purchase the right model for your circumstances!

Make sure you measure the square footage of the area you’d like to dehumidify, and invest in an accurate digital hygrometer, to calculate its relative humidity. A larger dehumidifier won’t hurt (except maybe your wallet), but one that’s too small will become a headache and less efficient.

So you’ve done your best to dehumidify your space without needing a dehumidifier, but now it’s time to bite the bullet.  Dehumidifiers come in all sorts of sizes, so how do you know which one you’re going to need for your space?

In this article, we’ll run you through how exactly dehumidifiers are rated for size, what you need to do to ensure that you’re purchasing the right one and any other factors you should bear in mind.

Come with us as we demystify the logistics behind dehumidifying your space appropriately!

How Dehumidifiers Are Sized

Let’s start with the basics: Totally safe to use, dehumidifiers are sized in a very particular way that considers the room’s capacity or space it needs to cover. 

So let’s break this down since it can be tricky to get your head around!

Your humidifier’s size relates to the total amount of moisture it can remove within 24 hours

This means that a 30-pint humidifier, in ideal testing conditions, can remove 30 pints of moisture per day from a space. The current testing conditions are at 65ºF, with 60% humidity. It’s essential to bear this in mind, as your room will likely differ from these conditions, so your results will vary.

If you have the area size in square feet that you’re hoping to place the dehumidifier in, you’ll be able to work out what size dehumidifier you’ll need. 

This is because the dehumidifier’s capacity roughly indicates the square footage of a space from which it can successfully remove moisture. Bear in mind that depending on how saturated the moisture in the room is, plus the temperature, effectiveness will vary somewhat. It also doesn’t hurt to have a slightly larger dehumidifier than needed, whereas a smaller dehumidifier could prove cumbersome.

How to Measure Your Room (and Calculate Humidity)

When you’re considering what size dehumidifier you’ll need, you’ll need to do two things:

Step 1️⃣ – Measure the square footage of the room you want to place the dehumidifier in

To calculate the square footage of your room, you’ll need to do some basic math. 

The square footage is calculated by multiplying the room’s length by the width. For example, if your room measures 12 feet by 20 feet, the total square feet of the room will be 240 square feet (12ft x 20ft = 2402ft).

Complete this calculation for any additional rooms you may need to place a dehumidifier in.

Step 2️⃣ – Calculate the relative humidity of the room.

Hygrometers (available to purchase online and from your local hardware store) measure humidity in the air. You can use them to measure just how much moisture is in the room you wish to dehumidify, which will help you choose the correct size dehumidifier for your space. 

Digital hygrometers will give you the most accurate results but are a little more expensive.

  1. Install your hygrometer on a wall at least five feet off the ground. Make sure it’s not in direct sunlight or close to a heat source, as this could affect your reading.
  1. Give the hygrometer at least five minutes to adjust before taking a reading. Leave the room for this step, as the temperature of your body and your breathing could affect the results.
  1. Check the hygrometer’s relative humidity percentage. Standard relative humidity will differ depending on where you live, but, as a rough guide, 40–60% in your home is considered a comfortable range.

This is the most accurate way to measure the humidity of a room. If you cannot purchase a hygrometer, there are various ways to measure the room’s relative humidity, including downloading an app on your phone.

The wet and dry bulb temperature test or the ice cube method are also ways to measure the humidity of a room. However, neither of these will accurately tell you the percentage of humidity. Instead, they will only be able to indicate whether or not there is a higher humidity level in your home.

How to Choose a Dehumidifier Size

Now that you’ve got your space’s square footage and relative humidity, it’s time to choose your dehumidifier. 

For rooms of around 600—1,200 square feet, you’ll need to look into a dehumidifier of around the same capacity. When operating in ideal conditions, these more powerful units can remove around 50—60 pints of water per day at a maximum.

Remember, a larger dehumidifier will never be an issue than one that is too small.

Danny’s Pick: HouseFresh Recommends

“When you have a large area, consider a model where you can drain it directly from the machine, either through a built-in hose or with a pump. That way, you won’t have to go back and forth emptying the tank. This hOmeLabs 4,500 Sq. Dehumidifier is perfect for large rooms and basements.”

Rooms of around 600—800 square feet will likely only need a medium-capacity dehumidifier as long as the room is only marginally damp or musty. 

Danny’s Pick: HouseFresh Recommends

“I recommend this Waykar Dehumidifier for medium sized rooms. It’s quiet, so it won’t disturb you. It has automatic settings so it’s super simple to operate. And most importantly, it can remove 34 pints in 24 hours. 

Finally, in smaller areas, about 600 square feet or less, a smaller-capacity dehumidifier should be adequate. However, this will depend on how damp your room is. Pricing will generally scale as the dehumidifier does, but some medium-capacity models can be equal in price to the larger ones. 

Danny’s Pick: HouseFresh Recommends

“This Midea Cube is perfect for smaller rooms. It’s a cool little device, but it has big capabilities. It will look great in a small space and can be expanded if you want to use it in a larger room.“

Remember that this all highly depends on how much humidity is in the air. An extremely wet room may need a more powerful dehumidifier to combat the moisture. In a 400-square-foot space that is significantly wet, medium-capacity dehumidifiers will also be a good call. These models, at ideal conditions, can remove around 30—39 pints of water in 24 hours.

In bathrooms, while dehumidifiers can be a great choice (and here are our 6 top dehumidifiers for bathrooms, plus the 1 you should avoid), adequate ventilation and extraction will also go a long way to helping get rid of excess moisture.

Dehumidifier Size Chart

When considering which dehumidifier to purchase, remember to take into account not only the size of the room and how damp it is. Here’s a handy chart to help you see at a glance what size dehumidifier you’ll need:

Room Dehumidifier (pint size)
Damp rooms of 500–1,500 square feet 24–39-pint
Very damp rooms of 500–1,000 square feet
Wet and extremely wet rooms of 500 square feet
Damp rooms of 2,000–2,500 square feet 40–59-pint
Very damp rooms of 1,500–2,000 square feet
Wet rooms of 1,000–1,500 square feet
Extremely wet rooms of 1,000 square feet
Very damp rooms of 2,500 square feet 60+ pint
Wet rooms of 2,000–2,500 square feet
Very wet rooms of 1,500–2,500 square feet

Final Thoughts

Dehumidifiers are rated according to how much moisture they can remove from a space over 24 hours. When choosing the size of your dehumidifier, you’ll need to consider both the size of your space and how damp it is to determine what dehumidifier will be most efficient accurately.

Remember that dehumidifiers, while excellent tools, will only affect the humidity in a room, not clean the air. To do that, you’ll need an air purifier.

To choose the best-sized dehumidifier for your space, don’t forget to do your prep work. Be sure to measure the square footage of the room, as well as the relative humidity, then check our chart to find the best model for your needs.