Dehumidifier Sizing Calculator

Measure the space, pick the description that matches how it feels — all three are ENERGY STAR's own wording — and the calculator returns the capacity range ENERGY STAR publishes for that combination, in pints per day under the current rating system, with the retail sizes that cover it. It returns a range and not a single number because a range is what is published. If the space runs cold, say so: a compressor dehumidifier below 65 °F collects a lot less water, which puts you at the top of the range rather than the bottom.

Data last updated: 2026-09-20

How this calculator works

Sizing is a table: how damp the space is on one axis, how big it is on the other, pints per day in the cells. ENERGY STAR publishes one — three conditions by two area bands — and the cells hold ranges rather than numbers: 20–30 pints for a slightly to moderately damp space under 2,000 sq ft, 25–40 if it is very damp, 30–50 if it is wet, and 30+, 40+ or 50+ above 2,000 sq ft. This calculator returns that range.

It used to return a single number, and that changed on 2026-09-20. The finer grid it interpolated — pints per day in 500 sq ft steps, attributed to AHAM DH-1 — existed here only as a third party's reproduction. No AHAM page was ever fetched to check it against, and a standards body's table would not be ours to reproduce from someone else's copy in any case. So the grid went, and with it the interpolation that gave the answer its false precision. Nobody publishes pints per square foot, and a calculator that prints "34 pints/day" where the only published figure is "25–40" is inventing the other nine. The range is less satisfying to read and it is what the evidence supports.

One trap: the pint numbers changed in 2019. DOE's test procedure moved from 80 °F to 65 °F to reflect basements, and every unit's rating fell. ENERGY STAR's own conversion table maps an old 70-pint to a new 40–45, an old 50 to a new 30. Retail listings say "50 pint (previously 70 pint)"; that's marketing rounding. This calculator speaks in new-rating pints; if you're comparing to an old unit's label, expect the number to look small.

Reading the result

• Capacity needed — the range ENERGY STAR publishes for your condition and your area band, in pints per day under the current rating. It is a range because a range is what is published; where to land inside it is a judgement, and the cold-space note below is the main thing that moves it.
• Retail size — 20/22, 30/35, or 50 pint. Above about 50 pints in one space, two units placed apart outperform one big one. Once you have a size, the electricity cost calculator estimates what it costs to run at your state's average rate.
• Pump? — if you chose a basement or a pump drain, a 50-pint-with-pump model saves the bucket routine; gravity drain to a floor drain is the cheaper equivalent when the floor cooperates.
• Cold-space note — under 65 °F, look for a unit that specifically advertises low-temperature operation and expect fan-only defrost periods; the not collecting water page explains what that looks like.