Enter the room and how damp it gets. You get the pints a day ENERGY STAR's chart asks for, what that number was on dehumidifier boxes before 2020, and how many certified models come in that size.
Your dehumidifier
A 20–30 pint dehumidifier for your 500 sq ft roomENERGY STAR: slightly to moderately damp, under 2,000 sq ft · pints a day under the 2019 DOE test (65°F) · about 30–50 pints on a label from before 2020
Quick answer: ENERGY STAR sizes a portable dehumidifier by how damp the room is. For a room under 2,000 sq ft, that is 20–30 pints a day if it is slightly to moderately damp, 25–40 if very damp and 30–50 if wet. Over 2,000 sq ft it is 30+, 40+ and 50+. These are today’s ratings: since 2019 the test runs at 65°F, so an old 50-pint box is about 30 pints now.
How to use the dehumidifier size calculator
- Measure the room: its length and width. ENERGY STAR’s chart changes only at 2,000 sq ft, so a rough size is enough.
- Say how damp it is: musty now and then (50–75% humidity), damp spots on walls and floors (75–90%), or walls that sweat and water that seeps in (90–100%). Say whether the room is often below 65°F.
- Replacing one? Add the pints on its old label, or the pints you empty each day. You get the pints a day to buy, what that was on boxes before 2020, and how many ENERGY STAR certified models come in that size.
Cooling the room too? The air conditioner BTU calculator sizes a window unit from ENERGY STAR’s own chart.
The rules, and where they come from
The chart. ENERGY STAR’s dehumidifier page: “The capacity you need depends on two factors: the size of the space that needs to be dehumidified and the conditions that exist in the space without dehumidification.” It says to “Use the charts below to estimate the minimum capacity for your portable dehumidifier”, and “it’s better to oversize than undersize!”
The new ratings. ENERGY STAR’s testing page: since June 2019 the DOE tests portable dehumidifiers “at 65°F, rather than 80°F, to more accurately reflect expected performance in a basement setting”. “There’s less water to remove in cooler air, which is why the capacities have decreased.”
Replacing one. “If you are replacing an existing dehumidifier, you can judge by how much water you empty each day.”
Cool rooms. “If the space being dehumidified has temperatures that typically fall below 65 degrees (F), you may want to consider buying a product that is specified for use at lower temperatures”: frost on the coils stops it removing water.
The target. “The optimum RH level for a building is generally considered to be between 30% and 50%. Anything above this range may promote mold growth.” Every certified unit has a humidistat to hold it there.
ENERGY STAR’s sizing chart
| The room without a dehumidifier | Under 2,000 sq ft | Over 2,000 sq ft |
|---|---|---|
| Slightly to moderately damp: musty at times, 50–75% humidity | 20–30 | 30+ |
| Very damp: damp spots on walls and floors, 75–90% | 25–40 | 40+ |
| Wet: walls or floor sweat, seepage, laundry drying, 90–100% | 30–50 | 50+ |
Pints of water removed a day, rated under the 2019 DOE test.
Old label to new rating
| Portable, old label (through 2019) | About today (2020 on) |
|---|---|
| 30 pints | 20 pints |
| 40 pints | 25 pints |
| 50 pints | 30 pints |
| 55 pints | 30–35 pints |
| 60 pints | 35 pints |
| 70 pints | 40–45 pints |
| 90 pints | 55 pints |
ENERGY STAR’s table, “a rough correlation … the actual change for specific models will vary”. Whole-home units: 80 → 70, 100 → 85, 120 → 100, 140 → 115, 160 → 135, 200 → 170.
The sizes you can buy
| Rated pints a day | ENERGY STAR certified portable models |
|---|---|
| 2–12 | 40 |
| 15–19 | 49 |
| 20–25 | 178 |
| 27–38 | 97 |
| 42–50 | 171 |
From data.energystar.gov, 4 October 2026: 535 portable models, none rated over 50 pints, and 148 rated exactly 50. The 24 certified whole-home units are rated 52–172 pints and are sized by a professional.
Worked examples
A 20–30 pint dehumidifier for your 500 sq ft room: a 25′ × 20′ basement that smells musty in summer. On a box from before 2020 that was 30–50 pints.
A 25–40 pint dehumidifier for your 1,000 sq ft room: a finished basement with damp patches on the walls. The chart is the same at 500 or 1,900 sq ft: the dampness decides.
A 50+ pint dehumidifier for your 2,500 sq ft space: a wet basement past the 2,000 sq ft line. No certified portable unit is rated over 50, so it takes two, or a whole-home unit.
At least a 45 pint dehumidifier for your 500 sq ft room: the old unit fills 45 pints a day, more than the chart’s 30. ENERGY STAR says to judge a replacement by what you empty.
Common mistakes
- Matching an old box’s number. A 70-pint unit from 2018 is about a 40–45 pint unit today: buying “70” now is not on offer.
- Sizing by square feet alone. Under 2,000 sq ft ENERGY STAR’s chart turns on how damp the room is, not its size.
- A cold basement. Below 65°F the coils frost; look for a model rated for low temperatures or with an anti-frost sensor.
- Leaving doors open. ENERGY STAR: close the doors and windows to the space while it runs.
More on damp rooms at Dreamy Home Style
- Cozy ideas for unfinished basements
- Basement laundry room ideas
- Basement bathroom designs
- Boho laundry room touches
Planning the basement itself? Draw it to scale in the free 2D floor planner.
Dehumidifier size questions
What size dehumidifier do I need?
Under 2,000 sq ft: 20–30 pints a day if the room is slightly to moderately damp, 25–40 if very damp, 30–50 if wet, by ENERGY STAR’s chart. Over 2,000 sq ft: 30+, 40+ and 50+.
What size dehumidifier for 1000 sq ft?
The same as for any room under 2,000 sq ft: 20–30 pints a day for a musty room, 25–40 for a very damp one, 30–50 for a wet one.
Is a small dehumidifier enough for a bathroom?
ENERGY STAR’s chart starts at 20 pints, though 89 certified models are smaller (9–19 pints). In a bathroom it advises a vent fan to remove the humidity at its source.
What is a large dehumidifier?
The largest certified portable units are rated 50 pints a day under today’s test; 148 models are. Above that, ENERGY STAR’s whole-home units run 52–172 pints and are installed by a professional.
Why are dehumidifier pint ratings lower now?
Since June 2019 the DOE tests at 65°F instead of 80°F. Cooler air holds less water, so the same machine is rated lower: an old 50-pint unit is about 30 pints.
Is it better to oversize a dehumidifier?
ENERGY STAR says yes: “it’s better to oversize than undersize!” The humidistat switches it off once the room reaches the humidity you set.