Dehumidifier Size Calculator
This tool helps you choose a dehumidifier size from the connected floor area and how damp the space is before drying. It also considers basements, indoor laundry drying, and cold rooms.
1Describe the space before dehumidification
Capacity ratings are tested near 65°F and 60% RH. A cold basement needs a unit that works at low temperatures and a safe drain plan.
Portable dehumidifier class
35 pints/day
The estimated need is about 21–31 pints per day.
Minimum starting capacity
21 pints/day
Preferred capacity
31 pints/day
Temperature check
Near the rating temperature
Modern ratings are often measured at 65°F and 60% RH.
A dehumidifier removes moisture from the air. It does not fix seepage, standing water, plumbing leaks, poor drainage, or unsafe mold. Open doors also connect nearby rooms to the area being dried.
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Quick planning answer
Portable dehumidifiers are rated by pints of water removed in 24 hours. ENERGY STAR guidance starts near 20 to 30 pints for a small or medium space that is somewhat damp. It suggests 25 to 40 pints for a very damp space and 30 to 50 pints when walls sweat or water seeps in.
Check the space before running the machine
A humidity meter helps, but its location matters. Keep it away from the dehumidifier's outlet air, outside walls, and damp air from laundry. If it is safe to leave the machine off, record morning and evening humidity for several days.
An open basement shares air through stairs and doorways. Include all connected areas and moisture sources, not only the small corner where the machine sits.
Good drainage keeps the dehumidifier working
A 50-pint rating describes water removal during a standard test. It does not mean the bucket holds 50 pints. If the bucket fills overnight and the machine stays off all day, the larger unit cannot help. Use a gravity drain with an air gap where allowed. Use an approved condensate pump when the drain must go uphill.
- Look for ENERGY STAR certification and the integrated energy factor.
- For a cool basement, look for low-temperature operation or defrost control.
- Choose a humidistat that agrees with a separate meter and can restart after an outage.
- Check filter access, fan noise, the hose connection, pump height, and how easily you can inspect the drain.
Fix water leaks before relying on a dehumidifier
Repair plumbing leaks, roof drainage, poor grading, sump failures, and active seepage. A dehumidifier can handle water vapor and normal moisture. It should not be the permanent answer to water entering through the foundation.
If visible growth covers a large area, materials stay wet, or sewage entered the space, get help from a qualified cleanup professional instead of choosing a larger machine. A dehumidifier also adds heat to the room, which may affect comfort upstairs.
Questions people ask before buying
What size dehumidifier do I need?
Use both the connected floor area and how damp it is. Current ENERGY STAR guidance places many small and medium spaces between 20 and 50 pints per day. Larger or wetter spaces may need more.
Is a 50-pint dehumidifier too big for a basement?
It is often a practical choice for a large or wet basement, especially with a continuous drain. The humidistat turns the unit on and off. Noise, frequent cycling, drainage, and cold-room performance still matter.
Does pint rating mean bucket size?
No. It tells you how much water the machine can remove in 24 hours under a standard test. The bucket is much smaller and may need to be emptied often.
Why does my basement dehumidifier ice up?
Cool air can make the evaporator drop below freezing. Look for low-temperature operation and defrost controls. Keep the filter and coil clean, and follow the maker's minimum room temperature.
Method, sources and limits
The tool starts with ENERGY STAR's current size ranges for small and medium rooms: 20 to 30 pints per day for somewhat damp rooms, 25 to 40 for very damp rooms, and 30 to 50 for wet rooms. It adjusts the result for areas up to and above 2,000 square feet.
The tool adds 5 pints for a below-ground basement and 5 pints for laundry dried in the space. It shows a warning below the common 65°F test temperature. The estimate does not measure active leaks or the full moisture load of an entire home.
- Dehumidifier sizing and buying guidance (ENERGY STAR)
- Dehumidifier efficiency criteria (ENERGY STAR)
- Moisture control guidance (U.S. Environmental Protection Agency)