dehumidifier sizing chart in order to size a dehumidifier

What Size Of Dehumidifier Do I Need? (Dehumidifer Sizing Chart)

Correctly sizing a dehumidifier is the first thing you need to do. The capacity of most residential dehumidifiers ranges from 30 pints to 70 pints.

Can a dehumidifier be too big? Of course. If you buy one that’s too big or one that’s too small, you will either be left with a high device/electricity cost or a still humid home.

When homeowners try to size a dehumidifier, we usually decide how big a dehumidifier we need based on what we need it for. In short, we incorrectly size a dehumidifier according to:

  • If we need it for the basement. Basements have high relative humidity; 70% to 100%, and low square footage. Dehumidifiers are perfect to extract that moisture.
  • If we need it for the whole house. Houses usually have 50% to 70% relative humidity and higher square footage.

What really matters for what size of dehumidifier we need are 3 specific factors:

  1. Relative humidity rates. They range from 50% to 100%. The purpose of using a dehumidifier is to lower relative humidity to 30% to 50%.
  2. Square footage. A smaller area (under 500 sq ft) will obviously need a smaller capacity of the dehumidifier (30 or 50 pints) than a bigger 1000+ sq ft areas. 
  3. Average temperature. Temperature is the most overlooked factor when it comes to what size of a dehumidifier you need. 

Most homeowners have a specific situation. Picking the correct size of a dehumidifier is not the simplest task in the world. However, we will help you at least get a rough estimate of how big a dehumidifier you need for your basement or house.

The most useful resource is the dehumidifier sizing chart. AHAM (Association of Home Appliance Manufacturers) has come up with directives on the capacity of dehumidifier for different relative humidity and area sizes.

You can jump to the sizing chart here.

2 Sizing Standards Currently In Use By Department Of Energy

One thing to be aware of before checking the sizing chart and using the calculator. As adopted by the Department of Energy (DOE), there are 2 testing standards for modern dehumidifiers:

  1. Old standard from 2012. 
  2. New standard adopted in 2019.

If you looked at any dehumidifier – you can check the best dehumidifier currently on the market here, for example – you will see something like ‘Midea MAD50C1ZWS Dehumidifier New 50 Pint-2019 DOE (Previous 70 Pint)‘.

Why does a dehumidifier that had a capacity of 70 pints have a new capacity of 50 pints? The device is the same; what changed is the DOE sizing standard.

The old 2012 standard took into account Energy Factor. The new 2019 standard takes into account the Integrated Energy Factor that is more accurate in representing the capacity of a dehumidifier. The new 2019 testing procedure also test dehumidifier at a lower temperature (65°F) while the older standard test temperature was 80°F.

That’s why both dehumidifier sizing chart and dehumidifier size calculator include both old and new capacity.

Here is a quick graphic representation of how old vs. new sizing standards differ. The example is made for a 500 sq ft area (room/basement/house):

Let’s look at the 75% relative humidity. According to the old standard, you would need a 50-pint dehumidifier. However, according to the new standard, you would need a 30-pint dehumidifier.

After 2022, only the new standard will be in use. Up that time, both standards are in use.

Dehumidifier AHAM Sizing Chart

Let’s start with the capacity of the dehumidifier. You can get a small 30-pint, a medium 50-pint, or the strongest residential 70-pint dehumidifier. This just tells you the maximum amount of water (in pints per day) a dehumidifier can squeeze out of your air per day, according to the tests made by DOE.

A pint is a weird unit; it amounts to 1/8 of a gallon. In short, the big 70-pint dehumidifier can absorb almost 9 gallons of water out of the house or basement air per day.

How big dehumidifier you should buy?

Here is a quick look at the Association Of Home Appliance Manufacturers (AHAM for short) table. You need to know how many sq ft of space you have and how humid those spaces are:

AHAM Dehumidifier Capacity Table

Humidity Levels:300 sq ft space500 sq ft space800 sq ft space1,200 sq ft space
50-60% Humidity
(Air feels
slightly heavy)
30 Pint (Old Standard)
20 Pint (New Standard)
45 Pint (Old Standard)
30 Pint (New Standard)
60 Pint (Old Standard)
40 Pint (New Standard)
70 Pint (Old Standard)
50 Pint (New Standard)
60-70% Humidity
(Occasional
musty smell)
30 Pint (Old Standard)
20 Pint (New Standard)
45 Pint (Old Standard)
30 Pint (New Standard)
60 Pint (Old Standard)
40 Pint (New Standard)
70 Pint (Old Standard)
50 Pint (New Standard)
70-80% Humidity
(Wet spots
on walls or floor)
40 Pint (Old Standard)
25 Pint (New Standard)
50 Pint (Old Standard)
30 Pint (New Standard)
65 Pint (Old Standard)
45 Pint (New Standard)

80 Pint (Old Standard)
55 Pint (New Standard)
80-100% Humidity
(Seepage on walls, mold possible)
45 Pint (Old Standard)
30 Pint (New Standard)
60 Pint (Old Standard)
40 Pint (New Standard)
70 Pint (Old Standard)
50 Pint (New Standard)
90 Pint (Old Standard)
60 Pint (New Standard)

For example, if you have a 500 sq ft basement with medium humidity (70%-80%), you would need a 50-pint dehumidifier. That’s a ballpark figure.

Note that some producers might be throwing around numbers like 3,000 sq ft or 4,500 sq ft. Long story short, it’s best to ignore those ‘calculations’. Here’s the real-life advice:

Always buy a big bigger dehumidifier. 70-pint ones are perfect for a majority of houses or basements.

Let’s look at 2 practical cases in order to get a grip on how to size a dehumidifier.

Example 1: 500 Sq Ft Basement With Very High Relative Humidity (80%)

Dehumidifiers are the most useful for very moist basements. Basements generally have an above-average humidity; this can spur spore and mold growth. In several decades, it can weaken the walls and put the whole structure of the house in danger.

Installing a dehumidifier makes a whole lot of sense. Here are the basic metrics of the basement (as an example):

  • Square footage: 500 sq ft.
  • Relative humidity: 80%.
  • Average temperature: 70°F.

If we check the dehumidifier sizing table above, we can see that the basement with these specs would need a 50- or 60-pint dehumidifier (according to the old standard) or 25-30 pint one (according to the new standard).

Whenever you have this kind of choice between a smaller (50-pint) and bigger (60-pint) dehumidifier, always use the one with higher capacity. It’s always better to have a more powerful dehumidifier than one that’s too weak to do the job.

Do keep in mind that AHAM sizing chart doesn’t take the average temperature in the account. If you have a cold basement, it makes sense to add 10 pints to the overall size of the dehumidifier.

Dehumidifiers have to work extra hard in colder environments.

Example 2: 1200 Sq Ft House With 65% Relative Humidity

One dehumidifier can be enough to lower the relative humidity in a small house. Compared to basements, the whole house has higher square footage but lower relative humidity.

That means a dehumidifier has to extract moisture from a larger volume of air. However, the amount of moisture in the air is overall lower.

Here are basic metrics for a small house (as an example):

  • Square footage: 1200 sq ft.
  • Relative humidity: 65%.
  • Average temperature: 70°F.

Checking the sizing table, we can deduce that such a house would need a 70-pint dehumidifier (old standard) or 50-pint one (new standard). For bigger spaces, you might want to look into the high-capacity commercial dehumidifiers.

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