Dehumidifier Size Calculator
Choose an area unit
The area is converted physically when you change unit systems.
Choose a portable dehumidifier capacity based on the floor area and how damp the untreated space feels. This calculator follows current ENERGY STAR room-buying guidance and reports its recommendation against current DOE-rated US pints per day, with liters per day for metric comparison. It provides a practical shopping range, not a guarantee that a unit will reach a particular humidity level or a substitute for whole-home moisture-load engineering.
How to estimate dehumidifier capacity
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1
Enter the floor area
Measure the connected space the portable unit must serve, then enter the area in square feet or square meters.
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2
Describe the untreated dampness
Choose damp, very damp or wet based on conditions before dehumidification, not the humidity setting you hope to reach.
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3
Read the capacity range
Compare current-rated pints per day and liters per day, then check the chosen model's operating-temperature range and drainage options.
How the estimate is determined
Dehumidifier capacity is the amount of water a unit removes in 24 hours under specified test conditions. It is not the tank size. This calculator applies the current ENERGY STAR dehumidifier guidance as a lookup table rather than inventing a continuous formula.
| Untreated space condition | Approximate relative humidity | Up to 2,000 ft² | More than 2,000 ft² |
|---|---|---|---|
| Damp to moderately damp | 50–75% RH | 20–30 US pt/day | At least 30 US pt/day |
| Very damp | 75–90% RH | 25–40 US pt/day | At least 40 US pt/day |
| Wet | 90–100% RH | 30–50 US pt/day | At least 50 US pt/day |
ENERGY STAR labels its two columns as below and above 2,000 ft² but does not assign the exact boundary. For a stable shopping convention, this calculator includes exactly 2,000 ft² in the lower-area range and switches to the larger-space minimum only above 2,000 ft².
For metric input, area in ft² = area in m² × 10.7639. For capacity, liters/day = US pints/day × 0.473176. The conversions change only the displayed units, not the recommendation band.
Worked examples
A 1,200 ft² basement that feels very damp falls in the 25–40 US pt/day band, equivalent to about 11.8–18.9 L/day. A wet 2,400 ft² open space falls in the larger-space category, so the result is at least 50 US pt/day, or at least 23.7 L/day. The second result deliberately has no invented upper limit; a large, open or multi-room layout may need a whole-home assessment.
Current ratings versus older labels
The US test procedure changed around 2019–2020 to use cooler, more realistic test conditions. Consequently, a current-rated unit can carry a lower pint number than an older model with similar real performance. Compare products using the same test basis. ENERGY STAR explains the rating change, while the US Department of Energy maintains the governing test framework.
Common pitfalls
- Sizing from area alone. Ceiling height, doors, airflow and continuing moisture infiltration affect real removal.
- Ignoring cold-room performance. For a cool basement or garage, check the manufacturer’s minimum operating temperature and automatic-defrost guidance.
- Treating dehumidification as a repair. Fix plumbing leaks, rain entry and groundwater first. EPA guidance recommends controlling the moisture source; a dehumidifier is not mold remediation.
- Expecting laboratory capacity every day. Actual water removal changes with temperature, starting RH, airflow and the selected humidity target.
- Using one portable unit as a whole-home design. Ducted systems and multiple connected rooms require equipment-specific or professional load assessment.
Frequently Asked Questions
It measures how much water the dehumidifier removes from the air over 24 hours under defined test conditions. It does not describe the collection bucket volume, and actual daily removal varies with temperature, humidity and airflow.
Only after checking the test basis. Current US capacity ratings use different, cooler test conditions than many pre-2020 labels, so the printed pint values are not directly comparable. Use the current rating shown in the product specifications.
No capacity estimate can guarantee mold prevention. EPA guidance is to keep indoor relative humidity below 60%, ideally around 30–50%, while repairing leaks and other moisture sources. Existing mold or water damage may require proper remediation.
There is no file upload. The values entered in this Livewire tool are sent to the server so it can calculate and display the recommendation. Do not enter personal or confidential information; only area, unit and dampness selections are needed.
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