Dehumidifier Size Calculator: How Many Pints per Day Do You Need?

A dehumidifier’s size is its capacity: how many pints of water it can pull out of the air in a day. The capacity you need depends on two things, according to ENERGY STAR: how big the space is and how damp it is without a dehumidifier. This calculator applies ENERGY STAR’s sizing chart to your space and, because the pint ratings on the box changed with DOE’s 2019 test, converts an old rating to the new scale.

How the calculator works

It looks up your space in ENERGY STAR’s chart for portable dehumidifiers:

Condition without a dehumidifier	Under 2,000 sq ft	Over 2,000 sq ft
Slightly to moderately damp: feels damp, musty smell that may come and go; 50–75% relative humidity	20–30 pints/day	30+ pints/day
Very damp: always feels and smells damp, damp spots on walls and floors; 75–90%	25–40 pints/day	40+ pints/day
Wet: walls or floor sweat, seepage, or high loads such as laundry drying; 90–100%	30–50 pints/day	50+ pints/day

A few choices fill the gaps in the chart:

• Humidity reading. If you enter a hygrometer reading, the calculator uses whichever row is wetter: your reading or the condition you picked. Where ENERGY STAR’s humidity bands meet (75% and 90%), it takes the wetter row.
• Exactly 2,000 sq ft. ENERGY STAR doesn’t say which column that falls in; the calculator uses the large-room column.
• Metric. Square meters are converted at 10.764 sq ft per m².

Both choices lean toward the bigger unit, because ENERGY STAR’s advice is that “it’s better to oversize than undersize”. Our guide to checking humidity in your house covers getting a reliable reading.

Note: You may see older sizing charts online with an “extremely wet” row and columns for 500 to 2,500 sq ft. They are not on ENERGY STAR’s current page, we couldn’t trace them to a primary source, and they predate the 2019 rating change, so this calculator doesn’t use them.

Worked examples

Space	What you see	Result
Basement, 800 sq ft	Musty smell, hygrometer reads 65%	20–30 pints/day
Basement, 1,500 sq ft	Damp spots on the walls, 80%	25–40 pints/day
Same basement, “moderately damp” picked	Hygrometer reads 80%	25–40 pints/day (the reading moves it to “very damp”)
Basement, 2,400 sq ft	Water seeps in at the floor, 92%	50+ pints/day
Basement, 70 m² (753 sq ft)	Feels damp, musty now and then	20–30 pints/day

Old vs new pint ratings: the 2019 DOE test change

If you’re replacing a dehumidifier bought before 2020, its pint rating isn’t comparable with a new one. DOE rewrote the test procedure in a 2015 rule, and the new energy standards that took effect in June 2019 are based on it:

• Old test: portable dehumidifiers were tested at 80 °F with 60% relative humidity (ANSI/AHAM DH-1-2008 conditions).
• New test: portable dehumidifiers are tested at 65 °F with 60% relative humidity. Whole-home dehumidifiers are tested at 73 °F and 60%. The current rules (10 CFR 430, Appendix X1) build on AHAM’s DH-1-2022 standard.

DOE chose 65 °F because it expected the average ground temperature during the dehumidifying season to be close to that, which makes it typical of a basement, and it found the condition representative of above-ground rooms too. DOE acknowledged that dehumidifiers remove less water at 65 °F than at 80 °F, which lowers the measured capacity. The energy rating changed at the same time, from Energy Factor to Integrated Energy Factor, which also counts the power used while the unit has cycled off.

ENERGY STAR’s rough conversion between the two scales:

Portable: old rating (through 2019)	New rating (2020)	Whole-home: old rating	New rating
30 pints/day	20	80 pints/day	70
40	25	100	85
50	30	120	100
55	30–35	140	115
60	35	160	135
70	40–45	200	170
90	55

ENERGY STAR says the actual change varies by model and the manufacturer may give a more reliable comparison. For an old rating between two rows, the calculator shows the span of both rows: an old 45-pint unit is about 25 to 30 pints, and an old 65-pint unit about 35 to 45. Outside 30 to 90 pints it doesn’t guess.

Worked conversions: an old 50-pint dehumidifier is about 30 pints on today’s scale, and an old 70-pint one about 40 to 45. So if a 50-pint unit kept your basement dry, a new 30-pint model may do the same job, as ENERGY STAR points out.

Tip: ENERGY STAR doesn’t say which rating scale its sizing chart assumes. Every dehumidifier sold new now carries the new rating, so we’d compare the chart with the number on today’s box and convert any old rating before comparing.

Getting the most from the dehumidifier

ENERGY STAR’s own tips:

• Close the doors and windows to the space while the dehumidifier runs.
• Give it room. Units without top-mounted air discharge need space from walls and furniture so air can circulate.
• Check the temperature. Below 65 °F, frost can form on the coils and the compressor can cycle without removing much moisture. For a cold basement or crawlspace, look for a model specified for lower temperatures; some have an anti-frost sensor.
• Plan the drain. A hose to a floor drain or sump saves emptying the bucket; keep hoses away from electrical cords.
• Set the humidistat. All ENERGY STAR dehumidifiers have one; the unit cycles on and off to hold the humidity you set.
• Look for the label. ENERGY STAR certified dehumidifiers use 20% less energy than similar conventional units. Efficiency is rated as Integrated Energy Factor in liters per kWh; higher is better.

Aim for EPA’s indoor range: below 60% relative humidity, ideally 30–50%. Our guide to the ideal indoor humidity explains why, and the dew point calculator shows when cold basement walls start to collect condensation.

A dehumidifier is one part of the fix

A dehumidifier treats the air, not the source of the water. Our guide on how to reduce humidity in your house starts with exhaust fans and leaks; the CFM calculator sizes a bathroom or kitchen fan. A dehumidifier also doesn’t filter anything: our comparison of an air purifier vs a dehumidifier explains which problem each one solves. For musty, spore-prone spaces, see our picks for the best air purifier for a basement and the best air purifier for mold, and remember EPA’s point: the key to mold control is moisture control, and mold that’s cleaned up without fixing the water problem will likely come back.