The capacity of most residential dehumidifiers ranges from 30 pints to 70 pints. The capacity of a dehumidifier vaguely indicates the size of the space it will cover in square feet. So, if you know the square footage of the area you want to dehumidify, you can get a good idea of the capacity you'll need. For example, a 20-pint dehumidifier is suitable for use in a 300 square foot room only while humidity levels are below 70%.
For higher humidity levels in a 300 square foot room, you will need a 25 or 30 pint dehumidifier to effectively reduce the humidity level. As you can see from the above information, it takes much more to determine the size of your optimal dehumidifier than the size of the room. For larger areas, such as basements, low spaces, or entire homes, you'll want to choose a dehumidifier based on whether your building is loosely, moderately, or hermetically sealed. The manufacturer calculates the paint capacity using a standardized test in which the unit is placed in a room with 60% humidity at 65 degrees.
Understanding which rating tells you what will help you find the right size of dehumidifier that fits your needs. Otherwise, if your space is smaller, look for a smaller model that's designed for the amount of square footage you're trying to dehumidify. If you often deal with excess moisture and see things like mold or smell musty, you need a whole house dehumidifier. Actually, given the standard conditions of 65 degrees and 60% humidity, a 30-pint dehumidifier is only suitable for rooms around 500 square feet.
Also test dehumidifiers at a lower temperature (65°F) than the previous standard test temperature (80°F). Fortunately, at higher temperatures, dehumidifiers are much more effective at removing moisture from the air than at lower temperatures. So, while you'd need a 50-pint dehumidifier in a 65-degree, 800-square-foot room, you could get away with a 40-pint unit if that same room averaged 80 degrees. With these four steps, you can determine the right size of dehumidifier for your room and how to measure humidity levels in a space.
You can also buy dehumidifiers for basements, dehumidifiers for small spaces and other dehumidifiers for single rooms.