What Size Humidifier Do I Need? (For 300 – 3,000 sq ft Room)

Cold weather means heating our living spaces – which leads to dryer air – which leads to the need to add moisture back into the air. This is what a humidifier does. Here is some information to help you decide what size humidifier you need.

Tips for Choosing a Humidifier

This guide is designed to help you select the right size humidifier for your room. To that end, here are important factors to consider.

The Total Size of the Area to be Humidified

When purchasing a humidifier, many people only think of adding moisture to the air in the room or rooms that need humidifying. They might simply choose a humidifier with a large tank and output. What they really need to consider is the total size of the particular area that needs humidifying – in other words, the volume of the space.

The usual method of determining the size of a room is to measure the length and width and then multiply. That is, a 10×12 foot room has an area of 120 square feet (10 times 12). However, when humidifying a room, the height also needs to be considered. The rating on most humidifiers is given in square feet, but assumes a ceiling height of 8 feet. This means that if your room is higher or lower than 8 feet, you will want to add or subtract approximately 10% to the size of the space you want to humidify.

For example, if you have a 20 x 15 bedroom, that’s 300 square foot. But if the ceiling height is 10 feet, you should add 10% to 15% to that number when looking for a humidifier to serve the room. Instead of one with 300 square foot capacity, consider those with 325 minimum and those designed for up to 350 or 375 square feet.

The Climate in Which You Live

Since it is the operation of heating equipment that causes the air in your home to be dry, it stands to reason that the more the heating equipment operates during an average day, the drier the air will be. Since a relative humidity level of 30% to 50% is considered ideal for the human body, you should choose a humidifier that has a moisture output near the maximum recommended in the charts below if you live in a very cold climate. If you live in a fairly moderate climate, you can choose a unit that is closer to the middle of the recommended outputs listed below.

Info tip: Dry air isn’t only caused by heating equipment. It is also a result of the fact that cold air can’t hold as much moisture as warm air – the colder the air, the less it can retain humidity. So, if your home isn’t well sealed, cold, dry air will infiltrate it while warmer, moist air will leave. The exchange of air has a definite drying effect. So, sealing windows, doors, air gaps, etc. around your home will keep more humidity inside – and that’s a great thing in winter.

Humidifier Size by Square Footage of Room

What size humidifier do I need for 250 – 3,000 sq ft room

Room SizeHumidifier Output
250 sq ft1.5 – 2.0 gallons per day
500 sq ft1.5 – 2.0 gallons per day
600 sq ft2.2 – 2.5 gallons per day
700 sq ft3 – 3.5 gallons per day
800 sq ft3 – 3.5 gallons per day
900 sq ft4 – 5.0 gallons per day
1,000 sq ft4 – 5.0 gallons per day
1,200 sq ft7 – 9.0 gallons per day
1,600 sq ft7 – 9.0 gallons per day
1,700 sq ft7 – 9.0 gallons per day
1,800 sq ft7 – 9.0 gallons per day
2,000 sq ft10 gallons per day
3,000 sq ft12 gallons per day

What size humidifier for 1000 sq ft?

4.0 to 5.0 gallons per day. If you find 1,000 sq ft in the left column, it is easy to see the corresponding humidifier size is 4-5 gallons/day.

What size humidifier for large room?

A humidifier with 3.5 to 4.0 gallon per day capacity is large enough for a large room up to 900 square feet, or around 30 x 30 or 36 x 25.

If you already know the square footage of the room you want to humidify, simply find that number in the left column (or the number closest to it), and you will see the output that your room size humidifier should have in the right column.

For example, if the size of a bedroom is 250 to 500 square feet, you should look for a humidifier with a moisture output of 1.5 to 2.0 gallons per day. However, if you have a large room, or perhaps a basement of 1,200 to 1,800 square feet, you will want to look for a humidifier with an output of 7 to 9 gallons per day.

Keep in mind what was mentioned above about your climate. For example, when considering what size humidifier for 1,000 square feet in upstate New York, it will need to have a higher output than one for the same size room in a town in the middle of Tennessee.

Humidifier Size by Length and Width of Room

How much moisture should the humidifier add to the air every day? Here’s what size you need based on the dimensions of the room.

Room SizeHumidifier Output
11x11 room1.5 – 2.0 gallons per day
11x12 room1.5 – 2.0 gallons per day
11x13 room1.5 – 2.0 gallons per day
13x13 room1.5 – 2.0 gallons  per day
14x14 room1.5 – 2.0 gallons per day
15x25 room1.5 – 2.0 gallons per day
16x20 room1.5 – 2.0 gallons per day
20x20 room1.5 – 2.0 gallons per day

What is the humidifier size for 12×11 room?

1.5 to 2.0 gallons per day. Find the closest dimensions in the left column – 11×12 – and glance to the right. You’ll see that a 12×11, or 132 square feet room, needs 1.5 to 2 gallons of output per day.

What size humidifier for bedroom?

A 1.5 to 2.0 capacity humidifier is the right size humidifier for a bedroom, according to the chart. This is because most bedrooms are 20×20 feet or less.

If you have the measurements of the room you want to humidify, simply find those measurements in the left column (or those closest to them), and you will see the output your humidifier should have in the right column.

Pro Tip: Remember to take the ceiling height into consideration as part of the total size of the area you want to humidify. Your decision for what size humidifier for a bedroom with a very high ceiling could be the same as the size humidifier for a large room with a fairly low ceiling. It’s the total volume – length, width and height that needs to be considered for proper humidification.

Room or Whole Home Humidifier?

With a few exceptions, humidifiers that sit on the floor or on a table are designed to humidify areas of 1,000 square feet or less. These are usually considered to be “room humidifiers”. This means that if you have a larger than average size apartment or a small to medium size house, you will need two or more room humidifiers to replace the dry air with that of a comfortable moisture content throughout your living space.

The better solution might be to purchase a “whole home humidifier”. These are usually installed directly into the warm air duct of your furnace, so the humidified air is circulated to all rooms in your house. These also have the added advantage of having a small water line connected directly to them. This means that there is no tank to fill or run dry, so it never stops providing humidified air to your whole house whenever the furnace is operating.

Room Size Humidifier FAQ’s

How many square feet does the Dyson humidifier cover?

Depending on the model you choose, Dyson humidifier air purifiers cover between 150 and 800 square feet.

Shouldn’t I just buy the largest size humidifier for my room? 

No. A humidifier that has a humidity output too large for the room it is in may cause several problems. Excess moisture may form on any cool surface, especially on windows. Mildew, mold, and bacteria may also begin to grow behind furniture or even draperies that are close to the walls. Know the size of the area that needs to be humidified and use the charts in this article to select the correct size humidifier for your needs.

Are there different types of room humidifiers? 

Yes. There are four basic types: Cool Mist, Warm Mist, Ultrasonic, and Evaporative Pad Humidifiers. Each has its pros and cons and may be better choices for different situations. For example, some sit on a table while others sit on the floor. Some are better for a small bedroom while others are better for a large living room. You can read about each of them in separate articles when determining what type of room humidifier is best for you.

A warm mist humidifier is a great choice for cold climates.

Never heard of an Ultrasonic humidifier? Here’s a page explaining a little about them and sharing the top models to consider.

Where should a humidifier be placed in a room? 

Set it in a central location where the moisture will be released into the air where air is flowing out of a grate.

Here’s the Pick HVAC guide called Where Should a Humidifier Be Placed?

What size humidifier for 3000 square foot house in Westchester County NY?

According to the chart above, a 3000 square foot home in Westchester County or any region of the Northern US needs a large humidifier with 10-12 gallon per day capacity.


Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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