How the Dehumidifier Sizing Calculator works
Last data update: 2026-09-20.
Data
One source: ENERGY STAR's "Recommended Capacity Range, pints per day" table, in pints per day under the 2019 DOE rating. All three condition descriptions are ENERGY STAR's own wording, including the relative-humidity bands.
| Condition without dehumidification | Under 2,000 sq ft | Over 2,000 sq ft |
|---|---|---|
| Slightly to moderately damp — space feels damp and has a musty odor that may be intermittent; 50–75 % RH | 20–30 | 30+ |
| Very damp — space consistently feels and smells damp, damp spots appear on walls and floors; 75–90 % RH | 25–40 | 40+ |
| Wet — walls or floor sweat, or seepage is present; high-load conditions such as laundry drying may be present; 90–100 % RH | 30–50 | 50+ |
Two things the table does not contain, and this page does not add. It has no area axis finer than that one 2,000 sq ft split, so there is no figure for 800 sq ft as distinct from 1,900. And above 2,000 sq ft it states a floor with no ceiling, which is why the calculator says "or larger" there rather than guessing a top.
The AHAM DH-1-2022-style grid used until 2026-09-20 has been removed, along with the third-party page that reproduced it. It was the last source on this site that was not the document's own publisher.
Formula
No interpolation and no arithmetic on the capacity figure: the condition and the area band select one cell, and the cell's range is the answer. Area over 2,000 sq ft selects the open-ended column.
Only the retail suggestion is computed, and it is a mapping onto sizes shops stock rather than part of the ENERGY STAR table. The range's low end picks the smallest class worth buying and its high end the largest the table asks for (≤ 22 pints → 20/22-pint class; ≤ 35 → 30/35; otherwise 50), so 25–40 reads as "30/35 to 50-pint class"; an open-ended cell reads as "or larger"; a basement or a pump drain adds the built-in pump. Where inside the range to land is stated as a judgement and labelled as ours: colder spaces at the top, heated living space near the bottom.
2019 rating change
DOE Appendix X1 (65 °F / 60 % RH) replaced Appendix X (80 °F / 60 % RH) for compliance from June 13, 2019 (background in 88 FR 48035). ENERGY STAR's conversion table: 30→20, 40→25, 50→30, 55→30–35, 60→35, 70→40–45, 90→55 (portable units).
Change log
- 2026-08-24 — first release.
- 2026-09-20 — the AHAM DH-1-2022-style grid and the third-party page that reproduced it were removed. The calculator now returns ENERGY STAR's published capacity range instead of a single interpolated number, the four dampness levels became ENERGY STAR's three (links shared with
damp=slightlyordamp=moderatelystill resolve, to the combined level), and floor area selects one of two bands at 2,000 sq ft instead of feeding an interpolation. Above 2,000 sq ft the answer is open-ended, because the table is.
Cite this page
GridComfort, "Dehumidifier Sizing Calculator — methodology," https://gridcomfort.com/tools/dehumidifier-sizing-calculator/methodology/, data updated 2026-09-20.