How to Use This Dehumidifier Size Calculator
Using this calculator takes about 30 seconds. Start by selecting your space type (basement, crawl space, bedroom, etc.), then enter the square footage of the area you want to dehumidify. Choose the dampness level that best describes your current situation - from slightly stuffy to visible standing water.
For a more precise recommendation, open the Advanced Options to set your ceiling height, drainage situation, whether you need to cover one room or multiple connected spaces, and any visible moisture severity signs like condensation, musty smell, or mold. Hit "Calculate" and you will get a recommended pint capacity, a safe size range, feature recommendations, and practical warnings if your situation calls for more than just a dehumidifier.
What Size Dehumidifier Do I Need?
Dehumidifier "size" is measured in pints per day - how many pints of water the unit can extract from the air in 24 hours. A 30-pint dehumidifier is not physically smaller than a 50-pint model; it simply removes less moisture per day.
The right size depends on three main factors: square footage, how damp the space is, and the type of room. A 500 sq ft dry bedroom needs far less capacity than a 500 sq ft wet basement, even though the square footage is identical. This is why a single number based on area alone is never enough - you need to account for the moisture load, which varies dramatically by room type, climate, and building condition.
As a general rule, undersizing is the bigger mistake. An undersized dehumidifier runs constantly without bringing humidity below 60%, which means mold, mildew, and musty smells persist. A slightly oversized unit simply reaches your target faster and cycles off, which is actually fine as long as it has a humidistat to auto-stop.
Every multiplier this calculator applies, including the dampness, space-type, temperature and coverage tables and the standard 20 to 70 pint sizes it rounds onto, is published in our dehumidifier sizing methodology.
How big of a dehumidifier do I need is a question about pints per day, and so is what pint dehumidifier do I need. What size dehumidifier should I get, or how do I know what size dehumidifier I need, has the same pint figure as its answer. The tool above does it whether you think of it as a dehumidifier calculator or a dehumidifier sizing calculator. If you only want to know how to size a dehumidifier by hand, it comes down to area, dampness and room type, in that order.
Dehumidifier Sizes Changed in 2019: Old Pint Ratings vs New
One fact explains most of the confusion over dehumidifier sizes. In 2019 the Department of Energy changed the test, and every pint rating printed since then is lower than it used to be for the very same machine. Units are now tested at 65°F, close to a real basement, where the old test used 80°F. Cooler air holds less water, so there is less to remove in a day. It is why the dehumidifiers sizes on shop shelves seemed to shrink overnight.
| Old Rating (through 2019) | Rating on the Current Test |
|---|---|
| 30 pints | 20 pints |
| 40 pints | 25 pints |
| 50 pints | 30 pints |
| 60 pints | 35 pints |
| 70 pints | 40 to 45 pints |
| 90 pints | 55 pints |
So when you ask what capacity dehumidifier do I need, first check which scale the advice is on. A guide written before 2020 that says 70 pints means a unit sold today as 50. The figures come from ENERGY STAR's page on dehumidifier testing and capacity, which also notes that the change for a given model can differ a little from this table.
Tip: when you replace an old dehumidifier, match the job and not the number on the old label. An old 50 pint unit that kept the basement dry is replaced by a current 30 to 35 pint one, and buying another 50 would be stepping up two sizes.
Dehumidifier Size Chart by Room Size and Dampness
Use this chart as a quick reference for recommended pint capacity. These figures assume standard 8-foot ceilings and a single open area above ground. Each one is produced by the calculator at the top of the page, so the dehumidifier room size chart and the tool always agree, and both use the current pint scale printed on units sold today. Adjust upward for crawl spaces, high ceilings, or visible moisture problems. Basements have their own chart just below.
| Room Size | Slightly Damp | Damp | Very Damp | Wet |
|---|---|---|---|---|
| 300 sq ft | 20 pints | 20 pints | 20 pints | 20 pints |
| 400 sq ft | 20 pints | 20 pints | 20 pints | 20 pints |
| 500 sq ft | 20 pints | 20 pints | 20 pints | 20 pints |
| 600 sq ft | 20 pints | 20 pints | 20 pints | 22 pints |
| 700 sq ft | 20 pints | 20 pints | 22 pints | 25 pints |
| 800 sq ft | 20 pints | 20 pints | 25 pints | 30 pints |
| 900 sq ft | 20 pints | 25 pints | 30 pints | 35 pints |
| 1,000 sq ft | 20 pints | 25 pints | 30 pints | 35 pints |
| 1,200 sq ft | 25 pints | 30 pints | 40 pints | 50 pints |
| 1,300 sq ft | 30 pints | 35 pints | 40 pints | 50 pints |
| 1,400 sq ft | 30 pints | 35 pints | 50 pints | 50 pints |
| 1,500 sq ft | 30 pints | 40 pints | 50 pints | 60 pints |
| 2,000 sq ft | 40 pints | 50 pints | 60 pints | 70 pints |
| 2,500 sq ft | 50 pints | 70 pints | 70 pints | 70 pints |
The chart stops at 70 pints because that is the largest standard portable size. Above 2,500 sq ft the calculator stops recommending a portable and points to a whole-house unit. A few cells show 22 pints: that is a real size on store shelves, one small step above the 20 pint models.
Basement Dehumidifier Size Chart
A basement needs 25% more capacity than a room of equal area upstairs, so it gets a separate table. What size basement dehumidifier do I need, or what size of dehumidifier do I need for my basement? This is the one to use. Read across from your floor area to the column that matches how the space feels and smells.
| Basement Size | Slightly Damp | Damp | Very Damp | Wet |
|---|---|---|---|---|
| 300 sq ft | 20 pints | 20 pints | 20 pints | 20 pints |
| 400 sq ft | 20 pints | 20 pints | 20 pints | 20 pints |
| 500 sq ft | 20 pints | 20 pints | 20 pints | 22 pints |
| 600 sq ft | 20 pints | 20 pints | 25 pints | 30 pints |
| 700 sq ft | 20 pints | 22 pints | 30 pints | 35 pints |
| 800 sq ft | 20 pints | 25 pints | 30 pints | 35 pints |
| 900 sq ft | 25 pints | 30 pints | 35 pints | 40 pints |
| 1,000 sq ft | 25 pints | 35 pints | 40 pints | 50 pints |
| 1,200 sq ft | 30 pints | 40 pints | 50 pints | 60 pints |
| 1,300 sq ft | 35 pints | 50 pints | 50 pints | 60 pints |
| 1,400 sq ft | 35 pints | 50 pints | 60 pints | 70 pints |
| 1,500 sq ft | 40 pints | 50 pints | 60 pints | 70 pints |
| 2,000 sq ft | 50 pints | 70 pints | 70 pints | 70 pints |
| 2,500 sq ft | 70 pints | 70 pints | 70 pints | 70 pints |
Some common cases, read straight off that table. What size dehumidifier for 800 sq ft basement use? 25 pints if it is damp, 30 if very damp and 35 if wet. A 700 sq ft basement needs 22, 30 or 35 pints on those three levels. For a 1000 sq ft basement the answers are 35, 40 and 50 pints.
Larger floors climb quickly. A 1500 sq ft basement takes 50 pints when damp and 60 when very damp. At 2000 sq ft a basement that is damp or worse is already at 70 pints, the top of the portable range, which is the point where two units or a ducted one start to make more sense than a single big box. A small basement under 600 sq ft is the opposite case: 20 pints covers it unless water is visible.
Dehumidifier Size by Square Feet: 400 to 2,500 Sq Ft
For rooms above ground, the smallest size goes a long way. At 400, 500 and 600 square feet a 20 pint unit is enough for a damp room, and that holds for 450 square feet and for a 12x12 room, which is only 144 sq ft. At 800 square feet the figure is 20 pints damp and 25 very damp. At 900 square feet it is 25 and 30.
For 1000 sq ft of living space the answer is 25 pints if damp, 30 if very damp. At 1200 square feet it rises to 30 and 40, and 1300 sq ft and 1400 sq ft sit at 35 to 50 pints across those two levels. At 1500 square feet plan on 40 pints damp or 50 very damp.
Past that, one portable is working at its limit. For 2000 sq ft the calculator gives 50 pints damp and 60 very damp, and for 2500 square feet it gives 50 pints only when the air is slightly damp and 70 for anything worse. Tip: size by square feet first, then move one column to the right for every sign of real moisture you can see or smell.
Dehumidifier Square Foot Coverage: 20 to 60 Pint Sizes
This is the same sum turned around. If you already own a unit, or one is on sale, the question becomes how much floor it can handle. The table shows the largest area the calculator still assigns to each size, to the nearest 25 sq ft. The area falls as the air gets wetter, so there is no single number per size.
| Size | Room, Damp | Room, Very Damp | Basement, Damp | Basement, Very Damp | Basement, Wet |
|---|---|---|---|---|---|
| 20 pint | 800 sq ft | 675 sq ft | 650 sq ft | 525 sq ft | 450 sq ft |
| 25 pint | 1,000 sq ft | 825 sq ft | 800 sq ft | 675 sq ft | 575 sq ft |
| 30 pint | 1,200 sq ft | 1,000 sq ft | 975 sq ft | 800 sq ft | 675 sq ft |
| 35 pint | 1,400 sq ft | 1,175 sq ft | 1,125 sq ft | 925 sq ft | 800 sq ft |
| 40 pint | 1,600 sq ft | 1,325 sq ft | 1,275 sq ft | 1,075 sq ft | 925 sq ft |
| 50 pint | 2,000 sq ft | 1,675 sq ft | 1,600 sq ft | 1,325 sq ft | 1,150 sq ft |
| 60 pint | 2,400 sq ft | 2,000 sq ft | 1,925 sq ft | 1,600 sq ft | 1,375 sq ft |
These are upper limits for an 8-foot ceiling and one open space. A taller ceiling, closed doors between rooms or a cool basement below 65°F all shrink the area, which is why the box on a store shelf often claims far more square feet than the unit will really dry.
40 Pint Dehumidifier Square Footage
How many square feet does a 40 pint dehumidifier cover? Up to about 1,600 sq ft of damp living space, or 1,325 sq ft if the room is very damp. In a basement the 40 pint dehumidifier room size drops to 1,275 sq ft damp, 1,075 sq ft very damp and 925 sq ft wet.
That makes 40 pints the natural size for a full basement under an average house, as long as water is not standing on the floor. If the old unit you are replacing was a 70 pint model bought before 2020, a current 40 to 45 pint one is its match, as the conversion table above shows.
Is a 35 Pint Dehumidifier Big Enough?
It is big enough for a damp basement up to about 1,125 sq ft, a very damp one up to 925 sq ft and a wet one up to 800 sq ft. Above ground, 35 pint dehumidifier room size reaches 1,400 sq ft of damp space. So is a 35 pint dehumidifier big enough for a basement? For a basement under 900 sq ft that has no standing water, yes.
The 35 vs 50 pint dehumidifier choice comes down to floor area and how wet the space is. A 50 pint unit carries a damp basement up to 1,600 sq ft and a very damp one up to 1,325 sq ft, 400 to 475 sq ft more than the 35 on those two levels. Tip: if your basement sits within 100 sq ft of the 35 pint limit for its dampness, buy the 50. A unit that runs flat out all day wears faster and still leaves the far corners damp.
20 and 30 Pint Dehumidifier Room Size
A 20 pint dehumidifier covers a damp room up to about 800 sq ft and a damp basement up to 650 sq ft. It is the right pick for a bedroom, a bathroom, a laundry room or a small basement, and it is the smallest standard size, so there is nothing to gain by looking for less.
The 30 pint dehumidifier room size is about 1,200 sq ft in a damp room upstairs, 975 sq ft of damp basement or 800 sq ft of very damp basement. In between, a 25 pint unit covers 1,000 sq ft upstairs and 800 sq ft below ground.
How Many Square Feet Does a 50 Pint Dehumidifier Cover?
About 2,000 sq ft in a damp room above ground, or 1,600 sq ft of damp basement, falling to 1,150 sq ft when the basement is wet. A 60 pint unit adds 225 to 325 sq ft to each basement figure. Beyond 60 pints the only standard portable left is 70, and a space that needs it is usually better served by two smaller units at opposite ends, or by a ducted whole-house model.
Best Dehumidifier Size for Basement, Crawl Space, Bedroom, and Apartment
Most people who land here have one room in mind, and it is nearly always below ground. So before the room-by-room notes, here is how to size dehumidifier for basement use in two steps. Work out the size as you would for any room of that area and dampness. Then add for the location: the calculator adds 25% for a basement and 35% for a crawl space, because the walls and floor keep feeding moisture into the air. That is the whole of sizing dehumidifier capacity for a below-grade space, and it is why what size dehumidifier for basement use comes out a step above the same room upstairs.
What Size Dehumidifier for a Basement
Basements are the most common space for dehumidifiers because they sit below grade, making them cooler and more moisture-prone than the rest of the house. Concrete walls and floors can absorb and release moisture constantly. Most basements in the 800-1,200 sq ft range need a 25-40 pint unit if damp, or a 35-60 pint unit if wet, on the current pint scale. Always look for continuous drainage (hose or pump) since basements generate ongoing moisture. The most common mistake is buying a small 20-pint bedroom unit for a 1,000 sq ft basement - it will run non-stop and never bring humidity under control.
What Size Dehumidifier for a Crawl Space
Crawl spaces are arguably the hardest space to dehumidify. They have minimal airflow, direct ground contact, and are often uninsulated. A crawl space dehumidifier should have auto-defrost (since crawl spaces can be cool), a built-in pump (since there is usually no floor drain), and be rated for the full square footage of the crawl space. If the crawl space is not encapsulated with a vapor barrier, a dehumidifier alone may not be enough - ground moisture will continuously refill the air faster than the unit can remove it.
What Size Dehumidifier for a Bedroom
Bedrooms typically need the smallest dehumidifier - a 20-30 pint portable unit handles most situations. Priority features are low noise (under 50 dB) and a humidistat to prevent over-drying while you sleep. The common mistake is ignoring the root cause: if a bedroom is humid, check for poor ventilation, a bathroom without an exhaust fan nearby, or a hidden leak behind the wall before assuming you just need a bigger unit.
What Size Dehumidifier for a Bathroom
Bathrooms generate spikes of humidity during showers. A dehumidifier is usually a supplemental fix when the exhaust fan is weak or absent. A compact 20-25 pint unit works for most bathrooms. However, the real fix is almost always a properly sized exhaust fan (50-110 CFM) vented to the outdoors, not into the attic.
What Size Dehumidifier for an Apartment
Apartments have unique constraints: shared walls help reduce temperature swings, but renters often cannot modify HVAC or drainage. A 20-35 pint portable unit with a tank (or a window drain hose) handles most apartment humidity issues. Focus on low noise and compact size since space is usually limited. In humid climates (Southeast US, Gulf Coast), even well-insulated apartments can benefit from a dehumidifier during summer.
What Size Dehumidifier for a Whole House
If your entire home has humidity issues, a single portable unit placed in one room will not cut it. For whole-house dehumidification, you have two options: a large 70-pint portable placed in the most central open area, or a whole-house dehumidifier tied into your existing HVAC ductwork ($1,000-$2,500 installed). The ducted option treats all rooms evenly and runs automatically, but requires professional installation. For homes over 2,000 sq ft with persistent humidity, a whole-house system is almost always the better investment.
Is It Better to Size Up a Dehumidifier?
In short: slight oversizing is usually the safer choice. Here is why:
- Undersizing is the bigger mistake. An undersized dehumidifier runs 24/7 without ever bringing humidity below 60%. The result is higher energy bills, faster wear on the compressor, and the mold/mildew problem never gets solved.
- A slightly larger unit reaches target humidity faster, then cycles off. As long as the unit has a humidistat (most do), it will stop running once humidity hits your set point. This means it does not over-dry the room - it simply works in shorter, more efficient bursts.
- Massive oversizing is unnecessary. Buying a 70-pint unit for a dry 300 sq ft bedroom wastes money on the upfront cost and offers no real benefit. Size up by one step (e.g., 30 pints → 40 pints), not three.
- When in doubt, size up for basements and crawl spaces. Below-grade spaces have unpredictable moisture loads that spike during heavy rains or snowmelt. A little extra capacity provides a safety margin.
Can One Dehumidifier Cover Multiple Rooms?
Yes - sometimes. A dehumidifier can effectively cover multiple rooms if:
- The doors between rooms stay open so air flows freely.
- The layout is relatively open-concept or has wide hallways connecting the spaces.
- The dehumidifier is placed centrally, not tucked into a far corner.
However, a single portable dehumidifier will struggle - or fail - to cover separate closed rooms. Air simply does not circulate through closed doors. In that situation, your options are:
- Use multiple smaller units, one per room.
- Keep doors open and use a fan to improve circulation.
- Install a whole-house ducted dehumidifier that treats air through the HVAC ductwork.
Placement matters more than most people think. Putting the unit near the source of moisture (e.g., near a sump pit, a wall with condensation, or a laundry area) will always outperform putting it far away in a dry corner.
Features to Look for Before You Buy
Not all dehumidifiers are equal. The features below can be the difference between a set-it-and-forget-it experience and one where you are constantly emptying a tank or troubleshooting frost buildup.
- Built-in pump: Essential for basements without a floor drain. A pump pushes water up to a sink, window, or utility line so you never need to empty a tank.
- Continuous drain hose: If you have a floor drain or a low-placed outlet, a gravity-fed hose lets the unit drain automatically. Cheaper than a pump but requires a downhill path.
- Auto-defrost: In cool spaces (basements, crawl spaces, garages), the evaporator coils can freeze. Auto-defrost cycles the compressor off to melt frost and keep the unit running efficiently.
- Washable filter: Saves money on replacement filters and keeps airflow strong. A clogged filter reduces dehumidification performance significantly.
- Tank size: If you cannot use continuous drainage, a larger tank (16+ pints) means fewer trips to empty it. Smaller tanks (8-10 pints) fill up quickly on 50+ pint units.
- Low-noise mode: Important for bedrooms, apartments, and living rooms. Look for units under 50 dB. Some models have a "sleep" or "quiet" mode that drops the fan speed.
- Energy Star certification: Energy Star dehumidifiers use 15-30% less electricity. Over a year of heavy use, this can save $40-$80 on your power bill.
- Humidistat / humidity control: A built-in humidistat lets you set a target humidity (e.g., 50%). The unit automatically cycles on when humidity rises above the target and shuts off when it reaches it. This prevents over-drying and saves energy.
When a Dehumidifier Alone Is Not Enough
A dehumidifier treats the symptom (excess humidity in the air) but does not fix the source. In several common situations, buying a bigger dehumidifier is the wrong answer:
- Active leaks: Water coming through walls or floors needs waterproofing, not a bigger dehumidifier. Fix the leak first.
- Standing water: If water pools on the floor after rain, address drainage - gutters, downspouts, grading, or a sump pump system.
- Poor exterior grading: If the ground slopes toward the foundation, water will constantly push into the basement. Re-grading the soil is the permanent fix.
- Major mold infestation: If mold covers large areas (over 10 sq ft), professional mold remediation should happen before or alongside dehumidifier installation.
- Foundation cracks: Cracks in the foundation allow water vapor and liquid water to enter. Epoxy injection or exterior waterproofing seals the entry point.
- Unencapsulated crawl spaces: A bare-dirt crawl space without a vapor barrier will continuously release ground moisture into the air. Encapsulation (6+ mil polyethylene sheeting, sealed vents) is the prerequisite - a dehumidifier is step two.
- Whole-house humidity beyond portable scope: If every room in a 3,000 sq ft home is humid, one portable unit cannot treat the entire home. A whole-house dehumidifier integrated with the HVAC system is the correct solution.
The goal of this section is not to scare you away from buying a dehumidifier - it is to make sure you spend your money where it will actually solve the problem. In many cases, a dehumidifier plus a targeted fix (like adding a sump pump or sealing a crawl space) is the right combination.
Related Air Quality & HVAC Tools
If your home suffers from the opposite problem, winter dryness, find the right equipment using our Humidifier Size Calculator. And if you are upgrading your HVAC system to better handle summer moisture, ensure your cooling equipment is properly sized with our main air conditioner size calculator. Both sizing tools sit alongside the rest of our indoor air quality calculators, which is the place to start if humidity is only part of what you are trying to fix.