Selecting the Perfect Dehumidifier Size for Your Basement

By: Evan Scoboria, Last updated: June 28, 2023

A damp basement can lead to various problems, such as mold growth, unpleasant odors, and damage to your home's structure. A dehumidifier is one effective way to tackle excess moisture in your basement. However, choosing the right size dehumidifier is crucial for optimal performance and energy efficiency. In this article, we'll discuss how dehumidifiers work, how to determine your basement's moisture level and size, and provide guidelines for selecting the perfect dehumidifier for your needs.

Understanding Dehumidifiers and Their Sizing

Dehumidifier on Basement Floor

How Dehumidifiers Work

Dehumidifiers are appliances designed to remove excess moisture from the air. They draw in humid air, cool it to condense the moisture into water, and then expel the drier air back into the room. The collected water is stored in a built-in container or drained continuously through a hose. Dehumidifiers come in various sizes and capacities, measured in pints of moisture removed daily.

Assessing Your Basement's Moisture Level

Before deciding on a dehumidifier size, it's essential to determine the moisture level in your basement.

Signs of Excess Moisture

Excess moisture in your basement can lead to various issues, including mold growth, unpleasant odors, and structural damage to your home. Here are some common signs that may indicate an excess moisture problem in your basement:

  1. Musty odors: One of the most common indications of excess moisture is a musty or moldy smell. This scent is often the first sign of a moisture problem and can indicate the presence of mold or mildew.

  2. Visible mold or mildew growth: Mold and mildew thrive in damp conditions. If you see mold or mildew growing on your basement's walls, floors, or other surfaces, it's a clear sign of excessive moisture. Mold often appears as black, white, or green spots.

  3. Condensation on windows or walls: Another sign of excessive moisture is condensation, which can form on cool surfaces when humid air comes in contact with them. If you notice water beads on your basement windows or walls, it can indicate a high humidity level.

  4. Damp spots on floors or walls: If you see unexplained wet spots, puddles, or signs of water staining on your basement floor or walls, it's likely a sign of a moisture problem.

  5. Peeling paint or wallpaper: Excess moisture can cause paint or wallpaper to peel or blister. If you notice these signs, it may be due to high humidity levels.

  6. Warped wood: Excess moisture can cause wood to warp, manifesting as swollen floorboards, doors that no longer close properly, or buckling hardwood floors.

  7. Rust on metal surfaces: If you have high humidity, you might notice rust forming on metal appliances, tools, or other items stored in your basement.

If you notice any of these signs, immediately taking care of the issue is essential to prevent further damage. Using a dehumidifier can help reduce the moisture levels in your basement. If the problem is severe or persistent, you may need to consider additional solutions, such as waterproofing or professional mold remediation.

Measuring Humidity Levels

A hygrometer or humidity sensor is typically used to measure humidity levels. These devices measure the amount of moisture in the air and present the value as a percentage known as relative humidity (RH). Relative humidity is the ratio of the current amount of water vapor in the air at a given temperature to the highest amount of water vapor the air can hold at that temperature.

Hygrometers can range from simple analog devices to more advanced digital models. Analog hygrometers use a moisture-sensitive material (usually human or animal hair) that expands and contracts based on the humidity, moving a dial to indicate the RH. Digital hygrometers, on the other hand, use electronic sensors to measure moisture and typically provide more accurate readings.

To use a hygrometer in your basement, place the device in the area you wish to measure and give it time to adjust to the environment. This usually takes a couple of hours. Then, read the RH value on the display. Measuring the RH at different times and areas of your basement is a good idea, as humidity can vary.

Ideally, the humidity level in your basement should be between 30% and 50%. Maintaining this range can help prevent mold growth and keep the environment comfortable. If the RH is consistently above this range, it's a clear sign that a dehumidifier could be beneficial.

Determining the Size of Your Basement

To determine the size of your basement to select the right dehumidifier, you need to calculate the total square footage. This simple process involves measuring the length and width of your basement and then multiplying those numbers together. Here's a step-by-step guide:

  1. Measure the Length: Use a tape measure to measure the length of your basement from one end to the other. Make sure to measure along the longest wall. Record this measurement in feet.

  2. Measure the Width: Next, measure the width of your basement. This measurement should be taken from one side to the other at the widest point. Record this measurement in feet as well.

  3. Calculate the Square Footage: Multiply the length of your basement by the width to calculate the total square footage. For example, if your basement measures 30 feet in length and 20 feet in width, the actual square footage would be 600 square feet (30 x 20 = 600).

Knowing the total square footage of your basement will help you choose the appropriate size dehumidifier, as manufacturers usually provide recommendations based on this.

Remember that if your basement has multiple rooms or areas separated by walls, you should measure each separately and then add the square footage together. Also, if your basement has a very irregular shape, you should divide it into smaller, regular shapes, calculate the area of each, and then sum those areas.

Remember, these measurements are used to provide a general guide. Other factors, such as the level of dampness in your basement, the number of windows and doors, and the overall airflow, can also influence the size of the dehumidifier you need.

Choosing the Right Dehumidifier for Your Basement

Dehumidifier Size Guidelines

The size of the dehumidifier you need for your basement largely depends on two factors: the size of your basement and the moisture level in your basement. Dehumidifiers are typically sized based on how much moisture they can remove from the air in 24 hours, measured in pints. Here are some general guidelines:

  1. Moderately Damp Basements (50-60% Relative Humidity): If your basement is only moderately damp but smells musty during humid weather, you should aim for a dehumidifier that can remove about 10 pints of moisture per day for every 500 square feet of space.

  2. Very Damp Basements (60-70% Relative Humidity): If your basement feels damp and smells musty all the time, or if you can see wet spots on the walls or floor, you may need a dehumidifier that can remove about 12 pints of moisture per day for every 500 square feet of space.

  3. Wet Basements (70-80% Relative Humidity): If your basement has visible water seepage or damp walls or floor, you will likely need a dehumidifier that can remove about 14 pints of moisture per day for every 500 square feet of space.

  4. Extremely Wet Basements (80-100% Relative Humidity): If your basement has had flooding issues or has visible water on the floor, you should aim for a dehumidifier that can remove about 16 pints of moisture per day for every 500 square feet of space.

Remember, these are general guidelines and may need to be adjusted based on specific factors such as the level of insulation, the number of windows and doors, and the overall airflow in your basement. Always refer to the manufacturer's guidelines and consult a professional if you need clarification.

Additional Factors to Consider in Dehumidifier Selection

Apart from size, there are other factors to consider when selecting a dehumidifier for your basement:

  1. Energy efficiency: Look for ENERGY STAR-certified dehumidifiers designed to consume less energy while providing optimal performance. This saves you money on electricity bills and helps reduce your carbon footprint.

  2. Continuous drainage: Some dehumidifiers have a continuous drainage feature, allowing you to connect a hose and direct the water to a drain, eliminating the need to empty the water container manually. This is particularly useful for larger basements with higher moisture levels.

  3. Built-in humidistat: A built-in humidistat measures the humidity level in your basement and automatically adjusts the dehumidifier's settings to maintain the desired humidity level. This feature ensures optimal performance and energy efficiency.

  4. Noise level: Dehumidifiers can generate noise during operation, which may be a concern if you spend significant time in your basement. Could you check the noise level rating of the dehumidifier before purchasing and opt for a quieter model if needed?

  5. Portability: Some dehumidifiers come with caster wheels, making moving the unit around your basement or between rooms easier. This feature may be helpful if you need to target specific areas or plan to use the dehumidifier in other parts of your home.


Selecting the right size dehumidifier for your basement is essential for effectively controlling excess moisture, preventing mold growth, and maintaining a healthy living environment. By understanding how dehumidifiers work, assessing your basement's moisture level and size, and following the guidelines, you can choose the perfect dehumidifier for your needs. Additionally, considering factors such as energy efficiency, continuous drainage, built-in humidistat, noise level, and portability can further enhance the performance and convenience of your dehumidifier. You'll be well on your way to a dry and comfortable basement with the right dehumidifier.