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Dehumidifier Size Calculator: AHAM Pints and Litres per Day
Estimate water-removal capacity from the historical AHAM sizing chart. Enter floor area, or volume and height, choose the dampness level and see how older pint ratings differ from current DOE labels.
Dehumidifier Size Calculator: AHAM Pints and Litres per Day: Selects the next area column in the AHAM 2005 chart: 500, 1000, 1500, 2000 or 2500 square feet. The result is a historical 80 °F, 60% relative-humidity rating, expressed in US liquid pints and litres per day. Volume divided by height supplies floor area; it does not add a volume multiplier. For cooling rather than drying, use the [air conditioner size calculator](/air-conditioner-size-calculator). Runs 100% locally in your browser with zero server file uploads.
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Formula: area = volume ÷ height; choose the next AHAM area column at or above 538.2 ft². Litres/day = pints/day × 0.473176473.
Area: 50 m² / 538.2 ft². The 1000 ft² column is used. Below 500 ft², use the smallest column; above 2500 ft², seek a separate assessment.
This is the historical 80 °F (26.7 °C), 60% RH rating. From June 2019, DOE tests portable units at 65 °F (18.3 °C), 60% RH. Lower pint ratings can describe comparable machines. Do not use a fixed conversion factor or compare this result directly with a modern label.
| Condition | 500 ft² / 46.45 m² | 1000 ft² / 92.9 m² | 1500 ft² / 139.35 m² | 2000 ft² / 185.81 m² | 2500 ft² / 232.26 m² |
|---|---|---|---|---|---|
| Moderately damp: occasional musty smell | 10 | 14 | 18 | 22 | 26 |
| Very damp: persistent damp patches | 12 | 17 | 22 | 27 | 32 |
| Wet: condensation or seepage | 14 | 20 | 26 | 32 | 38 |
| Extremely wet: wet floor or drying laundry | 16 | 23 | 30 | 37 | 44 |
AHAM 2005 selection guide, Table 1, published by Cornell Cooperative Extension. Conditions describe the space during warm, humid weather; no ceiling-height assumption is specified. Volume input only recovers floor area. Chart source
ENERGY STAR gives approximate old → new portable ratings: 30 → 20, 40 → 25, 50 → 30, 70 → 40–45 US pints/day. These examples vary by model. DOE rating change
Repair leaks and water ingress first. This sizing guide does not model ventilation, temperature, infiltration or ongoing moisture generation.
Historical AHAM chart
Cornell Cooperative Extension, Selecting a Dehumidifier, Table 1, citing the 2005 AHAM Directory. Columns cover 500–2500 ft² (46.45–232.26 m²), with four qualitative dampness levels during warm, humid weather. Source: https://cceschuyler.org/resources/selecting-a-dehumidifier
New DOE rating conditions
ENERGY STAR explains the 2019 test change for portable dehumidifiers from 80 °F (26.7 °C) to 65 °F (18.3 °C). Its approximate old-to-new examples include 30 to 20, 50 to 30 and 70 to 40–45 pints/day; model-specific comparisons vary. Source: https://www.energystar.gov/products/dehumidifier_testing_and_capacity
How to use it
- Choose metric or US units and enter floor area, or room volume and height.
- Select the dampness that describes the untreated space.
- Read the next chart size and compare rating conditions before choosing a machine.
Privacy & limitations
Your room measurements stay in your browser.
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Frequently asked questions
Is this the pint rating on a new machine?
The chart uses the older 80 °F test. The DOE portable-unit procedure introduced in June 2019 uses 65 °F at 60% relative humidity, so comparable machines may have smaller rated capacities. There is no universal conversion factor.
What if my room lies between chart columns?
The calculator uses the next larger column. Small rooms use the 500 square foot column; spaces above 2500 square feet need a separate assessment. Repair water ingress and check the machine's operating-temperature range.
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