What size dehumidifier do you need?
Buy too small and it runs all day without getting the room under 50% humidity. Buy too big and you paid for capacity you never use. The sizing chart below comes from the Association of Home Appliance Manufacturers (AHAM) and is adjusted for the 2019 Department of Energy test standard that today's pint ratings use.
Recommended dehumidifier size
Sizing guidance only. A dehumidifier manages humidity. It doesn't fix a leak, foundation seepage, or mold already in the walls.
The sizing chart behind this calculator
AHAM published this chart for years and most retailers still use it. The numbers are the minimum pints per day the space needs removed. Today's labels use a cooler 65°F test than the old 80°F one, so a unit pulls more than its label says in a warm, damp basement. That is why matching the chart number to the label works out.
| Condition | 500 sq ft | 1,000 sq ft | 1,500 sq ft | 2,000 sq ft | 2,500 sq ft |
|---|---|---|---|---|---|
| Moderately damp | 10 | 14 | 18 | 22 | 26 |
| Very damp | 12 | 17 | 22 | 27 | 32 |
| Wet | 14 | 20 | 26 | 32 | 38 |
| Extremely wet | 16 | 23 | 30 | 37 | 44 |
Retail units today come in roughly 20, 22, 30, 35, and 50 pint sizes. For most basements a 35 or 50 pint unit is the safe pick.
Frequently asked questions
Why did a 70-pint dehumidifier become a 50-pint one?
In 2019 the Department of Energy changed the test conditions from 80°F and 60% humidity to 65°F and 60%. Cooler air holds less water, so the same machine pulls fewer pints in the test. A unit that said 70 pints in 2018 says about 50 today. Nothing about the machine changed.
What size dehumidifier do I need for a basement?
For a typical 1,000 to 1,500 square foot basement that feels damp, a 30-pint unit under the current rating covers it. If the walls sweat, you see mold spots, or you live in a humid climate, go to 50 pints. Cool basements also need a unit with a low-temperature rating so the coils don't ice up.
Is a bigger dehumidifier always better?
Within reason. A larger unit reaches the target faster and cycles off, which uses less power than a small unit running constantly. Going way oversized wastes money up front and can dry the air below 30%, which is uncomfortable and hard on wood floors.
Will a dehumidifier get rid of mold?
No. It keeps humidity below the point where new mold grows, which is the best prevention there is. Mold already in drywall, wood, or carpet stays there until it is cleaned or removed. See the mold removal guides.
How long should I run it after a leak?
Until the materials are dry, not just the air. That usually means 3 to 5 days with fans and a dehumidifier running continuously, and longer for subfloors and wall cavities. A moisture meter on the drywall and framing tells you when you are done. Use the mold growth timeline tool to see where you stand.
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