The living room of a home with a dehumidifier on the floor and homeowner resting up against the couch with her cat in front

Dehumidifiers come in various sizes, from a twenty-pint capacity to a seventy-pint capacity (11.4 to 40 liters). The capacity tells you the maximum amount of water you can expect the dehumidifier to collect from the air in a single day. 

Choosing the right size of dehumidifier for your space is an essential part of purchasing one. 

Dehumidifiers are sized based on the amount of space you want to eliminate moisture from and the amount of humidity in the air.

In this article, I’ll discuss how you can choose the correct sized dehumidifier based on these factors and more.

Let’s get started!

How Do You Correctly Size Your Home Dehumidifier?

To correctly size your dehumidifier, you’ll first need to measure your space.

For example, a smaller room will need a smaller dehumidifier and vice versa. Then you’ll need to estimate the amount of humidity in the area. From there, you can accurately choose a dehumidifier.

How Home Dehumidifiers Are Sized

Dehumidifiers are sized based on how much water they can pull out of the air in twenty-four hours.

The size you’ll need varies depending on the size of your space and the room’s humidity. 

As mentioned in the introduction, dehumidifiers come in various sizes, from twenty to seventy pints (11.4-40 liters).

You usually won’t need to go past sixty pints (34 liters), even for a room that has experienced water damage. 

To determine the right size for your space, you’ll need to measure the area in which it will operate. This varies from space to space.

For example, if you’re only using the dehumidifier in one room with closed doors, then only measure that space.

However, measure each room separately and combine the spaces if you’re expecting to use your dehumidifier in a central area, such as a living room, kitchen, or den. 

If you’re regularly leaving the doors open, factor in a larger dehumidifier to ensure the job gets done correctly. 

You’ll also need to determine the amount of humidity in the air. This measurement can be calculated one of two ways – through exact measurements or estimation.

If you want to know the precise humidity levels in a space, you can purchase a hygrometer like this ThermoPro TP50 Digital Hygrometer.

Promo photo of the ThermoPro TP50 Digital Hygrometer on a nightstand next to a bed
Courtesy of Amazon

There are a few different methods to estimate the humidity level if you don’t have a hygrometer:

1. The Ice Cube Method 

The ice cube method is fairly simple to conduct.

For this method, you’ll want to fill a glass with water and two to three ice cubes. Once filled, place the glass in an unoccupied area. 

As a side note, the kitchen is not recommended for this experiment since the vapors from cooking can affect the experiment. Movement also affects it, so we want to place it in an unoccupied space.

Check on the glass after about five minutes, and observe the amount of condensation.

If the glass contains condensation, your home’s humidity levels are likely very high.

On the other hand, if the glass has formed very little or no condensation, the air is likely relatively dry. 

2. The Wet and Dry Bulb Method

This method is a bit more complicated than the ice cube method, but it should also provide a more accurate humidity reading.

To do the Wet and Dry Bulb Method you’ll need a few materials.

We’ve provided a list below:

  • 2 bulb thermometers
  • Wet paper towel
  • Rubber band
  • Room temperature water
  • Cardboard

That’s it!

So, how do you test the humidity through this method? 

It’s pretty simple. All you need to do is grab your thermometers and wrap a paper towel that has been dampened with room temperature water around the bulb.

Make sure you fasten it with the rubber band to stay connected to the bulb. You won’t do anything special with the other thermometer. 

Next, you’ll lay the thermometers side by side on a piece of cardboard for five to six minutes. Afterward, head back in and check the temperatures. At this time, you can expect the thermometers to be reading two different values. 

Now comes the fun part: math.

You’re trying to calculate what is known as the depression value in this experiment.

To find the depression value, you’ll need to subtract the wet bulb temperature from the dry bulb temperature

Courtesy of Anaesthesia and Intensive Care Medicine

From here, it’s pretty easy. Just look up a relative humidity chart like the one outlined here, and compare the numbers. 

3. The Feel the Air Method

The final method to test the humidity is relatively straightforward and quick.

Unfortunately, however, it’s also the least accurate.

This technique simply tests how the air around you feels to you. Again, this can be inaccurate because each person will have a different opinion on how the air feels. Nonetheless, it’s a decent method to get a quick reading. 

If the air feels just a little heavy, chances are the humidity levels are still relatively low, between 50 and 60%.

However, if you’re beginning to experience a musty smell in your space, humidity levels are higher, likely between 60 and 70%. 

For most homes, the humidity won’t be above 70%.

However, if you notice wet spots on the floor or walls, it’s likely to rise up to 80%.

Of course, if water seeps through anywhere, it’s significantly higher – in the 90% to 100% humidity range – which is a real problem. 

Choosing the Right Size Dehumidifier

In general, if you’re choosing a dehumidifier off of room size alone, it would look like this: 

  • Small Room: 0-499 Sq. Ft. 
  • Medium Room: 500-999 Sq. Ft. 
  • Large Room: 1000 + Sq. Ft. 

A small room needs a smaller dehumidifier that holds between 20-30 pints (11.4 and 17 liters).

A medium size room would require a dehumidifier that fits between 30 and 50 pints (17 and 28 liters). Typically, a large room would need a dehumidifier that holds 50 pints or more. 

However, as mentioned, you also have to factor in the amount of humidity in the space.

If you choose based on room size alone, you’ll either end up with a lot of excess moisture in the air or really dry air from the dehumidifier removing too much moisture. 

Here’s a helpful chart to help you decide with a glance:

Humidity Levels
Light Humidity 50-60%20 Pints25 – 30 Pints35 – 40 Pints50 Pints
Moderate Humidity
20 Pints25 – 30 Pints35 – 40 Pints50 Pints
High Humidity
25 Pints30 Pints45 Pints55 Pints
Very High Humidity
25 – 30 Pints35 – 40 Pints45 – 50 Pints60 Pints

As you can see from the table above, how large of a humidifier you need can vary widely depending on the humidity levels inside the room. 

An important note to be aware of is that the chart is based on standard rooms within a well-insulated area. So let’s talk a moment about spaces that look a little different. 

Dealing With Crawl Spaces, Basements, and Poorly Insulated Areas

Crawl spaces, basements, and poorly insulated areas can be enormously challenging to dehumidify fully.

These areas attract moisture and pests, and once the mold starts growing, it feels like you can never get rid of it.

Often, these spaces are not well sealed, and water seeps in through cracks in the walls, windows, or floors when it rains.

It’s essential that these areas are well sealed and dehumidified because over half of the air circulating throughout the rest of your home passes through these areas first.

When it comes to spaces like this, there are a few steps you’ll need to take to eradicate the moisture:

1. Remove All Visible Sources of Moisture

In crawl spaces, you may find that water has consistently been leaking into the area.

Upon investigation, you may see condensation on the walls or even small puddles throughout the opening. 

A puddle of standing water in a crawl space
Courtesy of Foundation Repair

If you’ve found anything like this, the first thing you’ll want to do is eliminate as much moisture as you can. Place towels in the area, and try to mop up as much visible water as possible. 

Dehumidifiers are built to remove water vapor from the air, not to remove full puddles of water.

The dehumidifier will be working three times as hard this way, and you’re unlikely to be able to dehumidify the space fully.

2. Clean the Crawl Space or Basement

You’ll want this to be a thorough cleaning. It might even be good to look into hiring a professional for this part. 

Too often, especially with basements, we use them as storage for all sorts of items. These items stay in the space for years, sometimes wholly untouched.

 Stagnation is never a good thing. Pests find their way into the undisturbed area, leaving holes along the way—a perfect way for moisture to get into the space. 

If you find that the space has attracted mold and mildew, thoroughly scrub the area until all traces of fungus are gone. 

Remember, a large portion of the air you’re breathing in your home daily has cycled through these spaces.

If you don’t completely remove it the first time, the mold will reappear later once you’ve done all the work to get your dehumidifier set up. 

3. Seal Off the Room From Moisture

The final step in preparation you’ll want to take is to ensure the room is completely sealed off from moisture continuing to enter the space.

This can be done by either covering the entire area in a vapor barrier or by encapsulating the space. 

A moisture barrier installed on a basement floor in a home

If you aren’t sure what encapsulating a space looks like, here’s a quick overview. Essentially, you’ll be covering the entire area with a heavy-duty plastic that works as a moisture barrier, sealing off the foundation vents, and of course, installing a dehumidifier. 

For more information on encapsulating an area, check out this helpful article on crawl space encapsulation

4. Install a Dehumidifier

After everything has been cleaned and moisture eliminated to the best of your ability, the final step is to put a dehumidifier in the space. 

Plan to buy a slightly larger dehumidifier than you would get for a standard room.

For example, if your basement is the size of a medium room, you’ll probably still want to get a dehumidifier that can remove 50 pints of moisture daily.

There are also designated crawl space and basement dehumidifiers like this ALORAIR Basement/Crawlspace Dehumidifier on Amazon. These dehumidifiers are expensive, but they do a great job removing the moisture from particularly damp areas. 

A Few More Tips on Selecting the Right Size Dehumidifier

While we’ve tried to be as thorough as possible in selecting the best size dehumidifier for your space, we want to mention a few more things. 

First of all, if your home is in a really humid climate, for example, in a tropical environment, it’s best to size up the dehumidifier from the beginning. 

In geographical areas like this, there’s no real escape from the humidity, and you can expect there to be a lot more present than you would in a drier climate. So plan to add about 10 pints (5.7 liters) to the recommended size.

If placing your dehumidifier in a space shared by multiple people, plan to add about five pints (2.8 liters). More people means more moisture. Furthermore, add another five pints if the space has a lot of windows and doors. 

Finally, add five pints if the space is near a washer and dryer. Washers and dryers are notorious for attracting extra moisture.

Dehumidifier Sizes

Dehumidifiers come in different sizes and are categorized into small, medium, and large, as discussed below:

  • Small portable dehumidifiers: These are the most quiet, inexpensive and are ideal for smaller areas of up to 400 square feet (37.16 square meters). They are capable of removing up to 30 pints (14.20 liters) of moisture from the air daily. Therefore, they are ideal for small home offices, bathrooms, and pantries.
  • Medium portable dehumidifiers: These options are a bit costly and generate more noise than their small portable counterparts. They work efficiently in areas ranging between 400 and 800 square feet (37.16 and 74.32 square meters). Medium portable dehumidifiers can remove between 25 and 50 pints (11.83 and 23.66 liters) of moisture from the air daily.
  • Large portable dehumidifiers: These are powerful and ideal for areas measuring between 800 and 1,200 square feet (74.32 and 111.48 square meters). They are capable of removing up to 60 pints (28.39 liters) of moisture from the air daily.
  • Whole-home dehumidifiers: These can work perfectly for an entire room and are ideal for spaces between 1,200 and 5,000 square feet (111.48 and 464.52 square meters). You can rely on whole-home dehumidifiers to remove between 80 and 155 pints (37.85 and 73.34 liters) of moisture from the air daily.

Final Thoughts

Finding the right-sized dehumidifier is a fairly simple process.

Generally speaking, you’ll start by measuring your space and checking the humidity levels in the room, either through a hygrometer or through one of the DIY methods discussed.

From there, choose the dehumidifier that most closely matches the square footage of your room combined with the humidity levels, and remember to upsize if you live in a high-humidity environment or if the space is likely to attract extra moisture from washers and dryers or exits to the outside.

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