What Size Dehumidifier Do I Need?

Last updatedLast updated: July 24, 2021
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The presence of damp can spoil an otherwise perfect location. Damp cannot be ignored or hidden. If it is painted over it comes back worse than ever. The smell of mildew is bad, and unhealthy. This is why a decent dehumidifier is an essential home item for a variety of reasons.  We can need them for our health, and the health of our homes. Removing moisture from the air is important for people with lung conditions. Moisture removal also prevents dampness in any areas it might form. This prevents dampness from causing damage to your plaster and paintwork. You’ll be able to shift that musty smell in no time. Not to mention breathing easier! It’s not as simple as grabbing a dehumidifier you like the look of though. You have to ask yourself the question, what size dehumidifier do I need?

There is a wealth of choice in the buyers’ market for dehumidifiers. Size and function can be minimal and basic, the sort of device suited for a small job. For advanced dehumidifying needs, there are larger appliances with more functionality. Models are available that suit the home. Industrial-scale machines are also accessible. Before you make a decision about what you might buy, think about what size dehumidifier you need.

Why The Right Dehumidifier Size Is Important

Too big and you’ve needlessly overspent. It might result in higher electricity bills too. Too small and you’ll be unable to remove the moisture that’s causing you problems. Finding the right dehumidifier size involves consideration of several factors. Think about the type of room. Consider the area the dehumidifier needs to cover. Are there any special requirements for the room’s usage?

How To Determine What Size Dehumidifier You Need

A dehumidifier is measured in its capacity to remove moisture. This is always in the pints of water removed per twenty-four-hour period. A thirty-pint dehumidifier would suit moderate levels of damp in an average-sized room. If the damp was bad, or the room larger, a bigger dehumidifier would be required.

The Room Moisture Level Is an Important Factor

What Size Dehumidifier Do I Need?Humidity comes from Air containing moisture. When it gets hot water evaporates and we describe the air as humid, like before a storm. If the temperature is 20°C then it will hold more water than a cooler temp such as 10°C. Too much humidity means mold and dampness. Too little will make the air you breathe very dry. Dry air can cause illnesses such as respiratory failure and dry skin. Air that is too wet not only risks mold but is more expensive to heat. If the air is wet, the heating must warm the water in the air as well and this is expensive. Similar to a thermostat that measures the heat of a room is a ‘Hygrometer’. This is a device that shows a room’s moisture level.

A room’s moisture is its ‘relative humidity ‘ or rh. During the summer we want an rh level of 50. As the weather grows colder, we need less humidity. We need an rh of 30 during the winter. The average stats that a room’s moisture is measured by are 65f at 60% moisture.

Measuring The Room Size Correctly

The steps to measure the square footage of a room are quite simple. You’ll need measuring equipment and a calculator. Take the length and width of the space and then multiply them to find the total squared area. For example, if a room is 10 feet long and 11 feet wide the total area would be 165 square feet. If you need to work out an area larger than one room then add the sizes together for the total area. If the room suffers from serious damp then use the Hygrometer to work out the rh as well as the size of the area.

What Size Dehumidifier Do I Need?

Other Factors to Consider

Don’t just think about the moisture level and room size. Consider what the room is used for. Is it going to matter if it’s noisy? Does the size of the device matter for where it’s going to be put? A dehumidifier can help with dampness in a bathroom. It can also be used for the maintenance and regulation of moisture levels for specific needs. A gun cabinet or dry goods locker needs a dehumidifier to prevent moisture build-up and decay. Certain dehumidifiers are built for specific jobs only.

Association of Home Appliance Manufacturers Size Chart

The Association of Home Appliance Manufacturers (called AHAM for short) produces a chart of humidity levels to room sizes. It was most recently updated in 2020. It compares room sizes to average humidity. This is for people to work out their average requirements when buying a dehumidifier. You can refer to this table when choosing your own dehumidifier.

AHAM Dehumidifier Capacity Table

Humidity Levels: 300 sq ft space 500 sq ft space 800 sq ft space 1,200 sq ft space
50-60% Humidity

(Air feels

slightly heavy)

20 Pint (New Standard) 30 Pint (New Standard) 40 Pint (New Standard) 50 Pint (New Standard)
60-70% Humidity


musty smell)

20 Pint (New Standard) 30 Pint (New Standard) 40 Pint (New Standard) 50 Pint (New Standard)
70-80% Humidity

(Wet spots

on walls or floor)

25 Pint (New Standard) 30 Pint (New Standard) 45 Pint (New Standard)


55 Pint (New Standard)
80-100% Humidity

(Seepage on walls, mold possible)

30 Pint (New Standard) 40 Pint (New Standard) 50 Pint (New Standard) 60 Pint (New Standard)

Dehumidifier examples for different spaces

Here are examples of average spaces with humidifiers that would suit their conditions. We’re also going to look at some special cases. Basements and crawl spaces need different types of care to dry goods or gun lockers. A small dehumidifier will not make a difference to a large room.


What Size Dehumidifier Do I Need?Basements are more likely to have dampness and mold than anywhere else in your home. There’s a variety of different dehumidifiers available. Depending on the dampness of your basement means a light, to heavy-duty, dehumidifier. If it’s very wet down there, and the basement is large, you’ll want a dehumidifier that’s up to the job. Too small and it’ll stay damp, too big and it’ll cost too much to run.


What Size Dehumidifier Do I Need?A bathroom is an important place in the house. You want to avoid mildew and dampness, but it’s a room designed for getting wet. A bathroom is unlikely to be as large as a basement, but dehumidifying it is still essential. A big dehumidifier will take too much space and look cumbersome. You need to find a model that’s up to the job, but also compact enough to fit the room.

Crawl space

What Size Dehumidifier Do I Need?A crawl space is like a basement, too much moisture will affect your home structurally. Bad smells can rise up and if it is damp it cannot work as a storage space. Researching the best dehumidifier for the job is as important as measuring the area the dehumidifier must cover. It’s vital to consider if the dehumidifier is going to fit in your crawl space too. Don’t just measure the area and dampness. Take into account the size of the machine and the size of where it needs putting too. This is important for anywhere that the dehumidifier is going to be visible in. A large machine that sucks the moisture out of the air in a basement is less of an issue than the same machine in a bedroom.


What Size Dehumidifier Do I Need?Our bedrooms are important living spaces. We need them to be clean and fresh for comfort and health. A damp bedroom could cause health issues and is unpleasant. There are a range of dehumidifiers that would suit use in a bedroom. As well as considering what size dehumidifier you need, think about the noise level. A quieter machine will benefit you in the room where you sleep.

Laundry room

What Size Dehumidifier Do I Need?As well as health and moisture control, a dehumidifier can be used to dry clothing. There are lots of dehumidifiers that come with a clothes drying setting. If your dehumidifier does not have a built-in function it still helps to turn it on while drying clothes. There is no heat to damage fabrics like a tumble dryer might. A dehumidifier will prevent clothing from smelling musty if it doesn’t dry quickly. It is also better than relying on ventilation.

Gun safes and other special-use locations

What Size Dehumidifier Do I Need?You may well need a specific dehumidifier for a certain type of job. Specialist devices can regulate moisture to a specific level. A gun safe MUST be dry or the firearms risk damage. Paper can be kept so it doesn’t rot. Dry goods need regulated moisture so they preserve well. If you have somewhere that needs to be kept dry for essential reasons you need a bespoke device. These might be more expensive, but their compact design is ideal for such occasions.

Final thoughts

When considering what size dehumidifier do I need, we need to look at the area the humidifier is going to cover. We look at the device dimensions for where we plan to keep it. We look at how much moisture there is in the air. A small room, or somewhere not that damp, needs a basic dehumidifier. If the area is very wet, and the area to be covered is large, we want a heavy-duty model. Forward planning is important to avoid disappointment and failure to remove damp. Understanding the basics of calculating area and moisture levels is essential. We hope this information has been helpful and that you can breathe a little easier now. Or at least that your clothes are dryer.

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