What Size Dehumidifier Do You Need?

First, determine the square footage of the area you want to dehumidify. There’s a little math involved, but it’s really simple: Just multiply the length of your room by the width.

Use this guide to help you choose the right dehumidifier size for your space. These figures—and Consumer Reports’ test results—rely on Department of Energy labeling standards updated in 2019 to more accurately reflect how well dehumidifiers work in basements, where many of these units are used. (You can learn more about them in our dehumidifier buying guide.)

If you can’t find a mention of the 2019 standard on the packaging or product information guide, check the model page on the manufacturer’s website. The retailer’s page may also display the information in the product details.

If the area is large—1,200 square feet or more—determining the right-sized dehumidifier is easy. Whether the room feels slightly damp or there’s noticeable condensation, you’ll need a powerful unit to dry the air. Large-capacity dehumidifiers can do that in all but the wettest situations. 

They can remove up to 50 to 60 pints per day. With that much liquid—50 pints is more than 7 gallons—it’s useful to have the water flow directly into a drain so you don’t have to empty the tank again and again. Models typically include a coupling that lets you attach a standard garden hose and direct the water into, say, a floor drain in your laundry room or a walk-in shower drain.

Models with a pump let you keep the humidifier on the ground and empty the water into a laundry sink. That’s a lot easier than lugging a full tank of water to the nearest drain. Most of the dehumidifiers in CR’s ratings don’t have a pump. But Misha Kollontai, the CR engineer who leads our dehumidifier testing, says you can often purchase a similar model with a built-in pump for about $30 more.

Pro tip: In a very big space, you might want to place a fan in another part of the room, too, to improve airflow and distribute the drier air throughout the area. Your dehumidifier’s fan might not be powerful enough for this job, Kollontai says, because these machines are designed to balance fan power and noise mitigation. 

Dehumidifiers in this category are designed to remove about 50 pints of water per day and are best for large spaces or medium-sized areas with persistent humidity problems.

If you have an area of 600 to 800 square feet that’s slightly damp or infused with a musty smell, a medium-capacity dehumidifier may solve your problem.

Wetter rooms as small as 400 square feet can also benefit from midsized units, which are designed to remove 30 to 39 pints of moisture per day. 

As a group, medium-capacity dehumidifiers are quieter than larger models, which is useful when you’re trying to dry out the air in a living area. You’ll typically pay somewhat less for a medium-sized dehumidifier, but some can cost as much as a large model.

Pro tip: Medium-sized rooms (between 600 and 1,200 square feet) that have small puddles, visible condensation, or mold need the same attention as a larger space. That means using a large-capacity dehumidifier, Kollontai says.

To see if your dehumidifier is up to the task, check the room’s humidity level with your hygrometer, then set up the dehumidifier and run it for a while, then check the humidity level once again, Kollontai says. On many dehumidifiers, you can see the relative humidity level in the unit’s built-in digital display. But it’s also a good idea to use that hygrometer you bought to take readings in different areas of the room to make sure the humidity is evenly distributed.

“If at full power your dehumidifier is only pulling your humidity down to 60 or 70 percent, you need a bigger dehumidifier,” Kollontai says.

Dehumidifiers we tested in this category can remove 30 to 35 pints of water from the air per day and are meant for midsized rooms that are somewhat damp. Of the medium-capacity dehumidifiers currently in our ratings, we recommend only one model.

Areas of less than 600 square feet usually call for a small-capacity dehumidifier. As you might expect, these remove less water and are less expensive than medium- and large-capacity models.

In CR’s ratings, the four recommended small-capacity dehumidifiers nab top marks in our water removal test. They also get strong or excellent ratings for noise—a key concern in a smaller space—and include a built-in fan. Only one has a pump.

Pro tip: In a bathroom, Lewis says, a good exhaust fan can be a better way to control humidity than a small-capacity dehumidifier. “That’ll suck all the moisture out in a few minutes,” he says.

These machines are designed to remove less than 30 pints of water per day. They work best at managing moisture in small spaces that are damp rather than truly wet.

Even the best dehumidifier won’t solve your problem if too much moisture from the outside is continually seeping into your home. Unclogging gutters and making sure downspouts are directing rainwater at least 5 feet from the foundation of your house can make a huge difference. If puddles and water droplets on floors, walls, and windows remain or worsen, contact a water remediation expert, an HVAC contractor, or a business that seals basements from moisture. 

If there’s too much moisture in most rooms in your house, you may be better off with a whole-house dehumidifier. (Consumer Reports doesn’t test these.) They’re available as portable units or as add-ons to an existing central heating and air conditioning system. Manufacturers say they can handle an area of up to 5,000 square feet. These units are expensive, but because they remove so much moisture from the air, they could enable you to cut back on air conditioning costs.

In some cases, you may need more than one solution, Lewis says. For example, if your basement has flooded, you��ll need to first remediate the damage and remove all the water, then install a dehumidifier to manage the residual moisture. And then take measures to prevent future flooding.

For musty crawl spaces—areas that are prone to mold growth—you might need an industrial-sized dehumidifier that can remove 70 or more pints of water per day. You can buy one on your own or through a contractor. These units typically have no tanks, so you’ll need to attach a drain line, Lewis says. For proper airflow, you also may need specialized ducts. Unless you’re handy, leave those tasks to a professional.