Dehumidifier Size Calculator
Enter the area and how damp it feels, and get the capacity to buy in pints per day on today's rating, what that equals on the old pre-2019 rating, and the watts a unit that size typically draws.
Dehumidifier size
C08Scenario A
Recommended capacity
A 30-pint unit on the 2019 DOE rating, sold as about 42 pints on the old rating.
- Recommended capacity
- 30 pints/day (DOE 2019 standard)
- Equivalent on the old (2012) rating
- ~42 pints
- Typical watts (rule of thumb)
- ~420 W
Estimate. Formula and sources are under “How it works”. Change any input; the result updates as you type.
Formula
How it works
The calculator looks up the AHAM sizing chart, by area and dampness, already converted to the 2019 DOE test standard:
| Pints/day (2019) | Up to 999 sq ft | 1,000–1,499 | 1,500–1,999 | 2,000–2,499 | 2,500+ |
|---|---|---|---|---|---|
| Slightly damp | 20 | 25 | 30 | 35 | 40 |
| Moderately damp | 20 | 30 | 35 | 40 | 50 |
| Very damp | 25 | 35 | 40 | 45 | 60 |
| Wet | 30 | 40 | 50 | 60 | 70 |
- Old (2012) equivalent ≈ 2019 pints × 1.4
- Typical watts ≈ 300 + 4 × pints
Since 2019, DOE tests dehumidifiers at 65 °F instead of 80 °F. Cooler air holds less water, so the same machine now removes fewer pints in the test. A unit labeled 50 pints today is roughly what used to be sold as a 70 pint.
Sources: sizing chart: AHAM DH-1 / DOE 2019 test procedure (10 CFR 430). Typical watts by capacity: ENERGY STAR dehumidifier product data.
Worked example
A worked example
A wet space of 2,200 sq ft falls in the 2,000–2,499 sq ft band of the chart, so it needs 60 pints a day on the 2019 standard. On the old rating that's ~84 pints. A unit that size typically draws ~540 W while running.
Questions
FAQ
What size dehumidifier for a 1,500 sq ft basement?
35 pints a day (2019 standard) if it's moderately damp, 40 pints if it's very damp. On the old rating those are about 49 and 56 pints.
Why do new dehumidifiers have lower pint ratings?
Because the test changed, not the machines. The 2019 DOE procedure measures water removal at 65 °F, closer to a real basement, instead of 80 °F. Multiply a new rating by 1.4 to compare it with an old listing.
Does a bigger dehumidifier use more electricity?
It draws more watts while running, typically about 380 W for a 20 pint unit and 580 W for a 70 pint unit, but it also reaches your humidity target sooner and shuts off. A unit that's too small can run all day. Use the Dehumidifier Cost To Run calculator with your watts and hours for the monthly cost.
What size for a small room or crawl space?
Anything up to 999 sq ft starts at 20 pints a day, or 25–30 if it's very damp or wet.
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