Dehumidifier Size Calculator
Pints per day on the current (2019) DOE scale.
Capacity
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Estimate based on the ENERGY STAR sizing chart. Pints per day on the 2019 DOE test (65°F, 60% RH).
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How dehumidifier sizing works
ENERGY STAR's chart gives a pints-per-day range by how damp the space is, for spaces under and over 2,000 sq ft:
| Condition | Under 2,000 sq ft | Over 2,000 sq ft |
|---|---|---|
| Moderately damp (50–75% RH): musty at times | 20–30 | 30+ |
| Very damp (75–90% RH): always feels damp | 25–40 | 40+ |
| Wet (90–100% RH): e.g. laundry drying | 30–50 | 50+ |
Within each range we move from the low end at 500 sq ft to the high end at 2,000 sq ft, then round up to a common size (20, 22, 30, 35 or 50 pints).
Why did dehumidifier pint ratings change?
From 2019 the DOE test moved from 80°F and 60% humidity to 65°F, closer to a real basement. The same machine removes less water in cooler air, so its rated pints dropped: an old 70-pint unit is now sold as roughly 40–45 pints. Older calculators and many forum posts still use the old numbers.
What size dehumidifier for a basement?
Under 2,000 sq ft, ENERGY STAR suggests 20–30 pints a day for a moderately damp space, 25–40 for a very damp one and 30–50 for a wet one, on the current scale. Bigger spaces need more, or a whole-home unit.
Is it better to oversize a dehumidifier?
Yes, within reason. ENERGY STAR says it is better to oversize than undersize: a bigger unit reaches the target humidity and then cycles off, while an undersized one runs nonstop and may never get there.
Sources: ENERGY STAR dehumidifiers; ENERGY STAR on the capacity rating change (old→new: 30→20, 40→25, 50→30, 70→40–45, 90→55).