How Many Pints Do I Need? A Dehumidifier Sizing Guide

What the pint rating means

A dehumidifier's capacity is measured in pints of water removed per 24 hours. The test conditions were updated by the U.S. Department of Energy in 2019, and portable models are now tested at 65 degrees Fahrenheit instead of 80 degrees, which more closely matches a basement setting. As a result, a new model may show a lower pint rating than an older unit even if it removes the same amount of moisture.

The capacity rating identifies how much moisture a dehumidifier can remove at those standard test conditions. It is not just a number on a box: it tells you whether the unit can keep up with the water being produced in your space. You can read more about capacity testing and why the old and new ratings differ in our explainer on pint ratings.

Two factors: room size and moisture level

The capacity you need depends on the size of the space that needs to be dehumidified and the conditions that exist in the space without dehumidification. Energy Star provides a simple chart that matches these two factors to a recommended range. The chart uses two room categories: small to medium rooms under 2,000 square feet, and large rooms over 2,000 square feet.

For each room category, Energy Star describes three moisture conditions. A space is 'slightly to moderately damp' when it feels damp and has a musty odor that may be intermittent. It is 'very damp' when it consistently feels and smells damp, with damp spots on walls and floors. It is 'wet' when the walls or floor sweat, seepage is present, or high-load conditions such as laundry drying are present.

The Energy Star sizing chart

Use the lower end for the smaller half of each room category and the higher end for the larger half. For example, a 1,200-square-foot living area that is only occasionally musty is closer to the 20-pint end, while a 1,900-square-foot space that feels damp most of the time is closer to the 40-pint end.

Energy Star notes that these are minimum recommendations and that it is better to oversize than undersize. If you have any doubt, choose the next size up rather than the next size down.

How to judge your moisture level

You can usually tell whether a room is damp just by spending time in it. Look for a musty smell, condensation on windows, damp spots on walls or floors, or a feeling of heaviness in the air. The CDC recommends keeping indoor humidity below 50% all day long to discourage mold growth, and an air conditioner or dehumidifier can help you keep the level low.

The EPA advises drying water-damaged areas and items within 24 to 48 hours to prevent mold growth. If you have had a recent flood, a leak, or you regularly see moisture collecting on surfaces, your space likely falls into the 'very damp' or 'wet' category of the chart. Mold can begin growing indoors when spores land on wet surfaces, so it is important to act before the problem spreads. See our guide on recommended humidity settings for more detail.

Why oversizing is safer

Energy Star explicitly states that it is better to oversize than undersize a portable dehumidifier. An undersized unit runs almost constantly without bringing the humidity down, which wastes energy and may not prevent mold. An oversized unit will cycle off once the target humidity is reached, so it does not keep running needlessly.

A larger unit may be bulkier and may use more energy when it is first pulling the humidity down, but it will do the job reliably. If you are between two sizes, pick the larger one. That advice is especially useful for basements and other spaces where moisture problems tend to be persistent.

Special cases: basements, crawl spaces, and low temperatures

Basements and crawl spaces often run cooler and damper than living areas. If the space routinely falls below 65 degrees Fahrenheit, frost can form on the condensing coils. That can reduce performance and cause the compressor to cycle on and off without removing much moisture. Some dehumidifiers have an anti-frost sensor that automatically turns the unit off if the air temperature drops below a certain point.

For these spaces, look for a model that is rated for low-temperature operation. Our basement dehumidifier guide and crawl space guide can help you compare models. You can also read more about low-temperature performance if your basement is cool in any season.

If you need to cover a very large area over 5,000 square feet, a single portable unit may not be enough. Check our over 5,000 sq ft guide for units in that class, or consider a whole-home system installed with your ductwork. Portable units are easy to move, but a whole-home dehumidifier is often the better match for multiple rooms. See our comparison of portable vs. whole-house dehumidifiers.

Replacing an older dehumidifier

If you are replacing a unit purchased before 2020, keep in mind that the pint rating on the new model will likely be lower because of the updated test procedure. Energy Star provides a rough correlation: an old 30-pint unit corresponds to a new 20-pint unit, old 50-pint to new 30-pint, and old 70-pint to new 40-45 pints. This does not mean the new unit removes less moisture in real conditions; it only reflects the cooler test temperature.

You can also judge your need by how often you emptied the old bucket. If the bucket filled quickly, the new unit should be at least as capable as the old model, but remember to compare using the new rating scale. For more on why capacity ratings changed, see Energy Star's testing and capacity page and our article on the DOE testing standard.

Control moisture sources before you choose

Even the right-size dehumidifier cannot do its job if you keep adding moisture to the air. The University of Minnesota Extension notes that everyday activities release moisture: people breathing, long hot showers, cooking with uncovered pots, drying clothes on an indoor clothesline, using humidifiers, and watering many plants can all raise the moisture level. Fixing those sources first makes your dehumidifier work more effectively.

The EPA and CDC both emphasize that the key to mold control is moisture control. Repair roof and plumbing leaks right away, use exhaust fans that vent to the outside, and dry out flooded areas within 24 to 48 hours. When you run a dehumidifier, do not leave windows open on damp days, since that lets outdoor humidity back in.

A dehumidifier is part of a complete moisture management plan, not a substitute for fixing leaks and improving ventilation. Once you have reduced the obvious moisture sources, the pint sizing chart becomes a much more reliable guide.

What to pick for your use

Questions

What does the pint rating on a dehumidifier mean?

It is the amount of water the unit can remove in 24 hours under standard test conditions. The Department of Energy updated the test to 65 degrees Fahrenheit in 2019, so new ratings are not directly comparable to old ratings.

Can a dehumidifier be too big for a room?

Usually not. Energy Star advises that it is better to oversize than undersize. An oversized unit will simply cycle off when the humidity reaches the set level, while an undersized unit may run constantly without solving the problem.

How do I know if my room is 'wet' or 'damp'?

Look for musty odors, damp spots, condensation, or a feeling of dampness. If you see water on walls or floors, that is the 'wet' category. Energy Star's chart also lists relative humidity ranges: wet is roughly 90% relative humidity or more.

Do I need a larger unit for a basement?

Basements often need more capacity because they are cooler and more humid. Also, if the temperature drops below 65 degrees Fahrenheit, you need a model rated for low-temperature operation or one with an anti-frost sensor.

What if I am replacing an old dehumidifier?

Use Energy Star's capacity change table to compare old and new ratings. For example, a new 20-pint unit is roughly equivalent to an old 30-pint unit, and a new 30-pint unit replaces an old 50-pint unit.

Should I consider a whole-home dehumidifier for a large house?

If you want to control humidity across multiple rooms, a whole-home unit installed by a professional may be more effective. See our guide to portable vs. whole-home systems for a full comparison.

Can I rely on the pint rating alone to choose a unit?

No. You also need to consider the room size, moisture level, temperature, and how the unit will be drained. A unit with a good pint rating may still struggle if it cannot handle low temperatures or if it has a small water bucket.

How high should I keep indoor humidity?

The CDC recommends keeping indoor humidity as low as you can and no higher than 50% all day long. Using a dehumidifier is one way to keep the level low, especially in damp basements.