Dehumidifier Size Calculator

The short answer

Size a dehumidifier by how damp the space is. For a space under 2,000 sq ft, ENERGY STAR recommends 20 to 30 pints a day when it’s slightly to moderately damp, 25 to 40 pints when it’s very damp and 30 to 50 pints when it’s wet. From 2,000 sq ft up, it’s 30 pints or more, 40 pints or more and 50 pints or more.

Those numbers are for dehumidifiers rated in 2020 or later. Older labels show bigger numbers for the same capacity, because the test changed, so the calculator can also convert an old rating into today’s terms.

How to use the calculator

1. Pick a mode. “Size a new one” finds the capacity for your space. “Convert an old rating” translates the number on an older unit, or in an older sizing guide, into a current rating.
2. Measure the space. Measure the room, or the whole basement or open area you want to dry, wall to wall.
3. Pick how damp it is. Go by how it feels and smells, or by a reading from a hygrometer (a small humidity meter).
4. Read the result. You get a range in pints per day. If you’re not sure, go toward the top of it.

Switch to metric with the toggle at the top. Use Copy link to save your result or send it to a roommate.

Dehumidifier size chart

ENERGY STAR’s recommended capacity in pints per day, for current ratings:

How ENERGY STAR describes each condition:

• Slightly to moderately damp: the space feels damp and has a musty smell that may come and go.
• Very damp: it always feels and smells damp, and damp spots show up on walls and floors.
• Wet: the walls or floor sweat, or water seeps in. Drying laundry indoors counts here too.

Old ratings vs. new ratings

Through 2019, dehumidifier labels came from a test at 80°F and 60% humidity. Under DOE’s current test procedure, portable dehumidifiers are tested at 65°F, with the same humidity. Colder air gives up less water, so DOE expected the same unit to measure lower. AHAM, the appliance makers’ association, estimated the drop at about 35% on average.

ENERGY STAR’s conversion table for portable dehumidifiers:

ENERGY STAR notes that the actual change varies from model to model, so for one specific unit, the manufacturer’s listing is the better guide. If an older guide tells you to buy a 50 pints dehumidifier, look for about 30 pints on a current label.

How we calculate

• Area: room length × width.
• Size column: ENERGY STAR’s chart has two columns, small to medium spaces (under 2,000 sq ft) and large spaces (over 2,000 sq ft). It doesn’t place a space of exactly 2,000 sq ft, so we count that as large, because ENERGY STAR says it’s better to oversize than undersize.
• Capacity: we show ENERGY STAR’s range for your condition and column as it is. We don’t narrow it with a formula of our own, because the chart doesn’t say how. For large spaces, the chart gives a minimum only.
• Converting: we look up your old rating in ENERGY STAR’s table for portable units. The table lists set ratings, so we don’t estimate anything in between, and whole-home units aren’t covered.

The chart doesn’t ask about ceiling height or temperature, so the calculator doesn’t either. Treat the result as a starting point and check how the room feels after a few days.

Worked examples

Example: A damp bedroom

What we know

• Space: 14 ft by 12 ft
• Condition: Slightly to moderately damp (50% to 75% humidity)

How it works out

1. Area: 14 ft × 12 ft = 168 sq ft.
2. 168 sq ft is under 2,000 sq ft, so it's a small to medium space on the chart.
3. ENERGY STAR's range for that space and condition: 20 to 30 pints a day.

Look for 20 to 30 pints a day on a current label, toward the top of the range if you're not sure.

Example: A very damp basement apartment

What we know

• Space: 30 ft by 25 ft
• Condition: Very damp (75% to 90% humidity)

How it works out

1. Area: 30 ft × 25 ft = 750 sq ft.
2. 750 sq ft is under 2,000 sq ft, so it's a small to medium space on the chart.
3. ENERGY STAR's range for that space and condition: 25 to 40 pints a day.

Look for 25 to 40 pints a day on a current label, toward the top of the range if you're not sure.

Example: An older 70-pint dehumidifier

What we know

• Old label: 70 pints a day (rated in 2019 or earlier)

How it works out

1. Find 70 pints a day in ENERGY STAR's conversion table for portable dehumidifiers.
2. The same capacity under the current test: 40 to 45 pints a day.

About 40 to 45 pints a day on a current label.

Bucket or hose?

Most portable dehumidifiers collect water in a removable bucket and shut off automatically when it’s full, ENERGY STAR explains. Some have a hose fitting, so you can drain the water into a floor drain or sump instead of emptying the bucket.

If you use a hose, put the unit close to the drain so the hose stays short and out of walkways. ENERGY STAR’s own tip: don’t create a tripping hazard. Replacing an old dehumidifier? ENERGY STAR suggests judging the new size by how much water you empty each day.

An ENERGY STAR certified model removes the same moisture with about 20% less energy than a standard one, according to ENERGY STAR, which matters if it runs all summer.

What a dehumidifier costs

In its 2024 review for the ENERGY STAR specification, EPA priced several portable models. The averages, from units at the federal minimum to ENERGY STAR certified ones:

The last column restates EPA’s electricity cost at the US average price for January to August 2026, from the U.S. Energy Information Administration. Prices are approximate and change with sales and models, so treat them as a starting point.

Renters: leaks, mold and your landlord

A dehumidifier dries the air. It doesn’t fix where the water comes from. EPA advises renters to report plumbing leaks and moisture problems to the building owner, manager or superintendent right away. If a persistent water problem isn’t fixed, EPA says you may want to contact local, state or federal health or housing authorities.

Damp spots, sweating walls and seepage are worth reporting before you buy anything. Keep a dated photo of the problem and a copy of your message.

The dehumidifier itself is about as low risk as an upgrade gets: it plugs in, it doesn’t touch the walls and it comes with you when you move.