Dehumidifier Size Calculator

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How to use this Dehumidifier Size Calculator

This tool estimates the dehumidifier size you need in pints of moisture removed per day. It’s designed for bedrooms, living rooms, basements, and utility spaces where humidity and musty smells are a problem.

1. Enter your room size.
   Type in length and width in feet, or switch to square footage if you already know the total area you want to dehumidify.

2. Describe how damp the space feels.
   A room that’s just a bit clammy in summer needs less capacity than a basement with a constant musty smell or visible condensation. Choosing the right “dampness” level has a big impact on the recommended pint rating.

3. Select room type and local climate.
   Basements, crawlspaces, bathrooms, and laundry rooms usually need more dehumidifier capacity than upstairs bedrooms. If you live in a humid or coastal climate, your dehumidifier will also work harder than in a dry region.

4. Add people and extra moisture sources.
   More people breathing in the space, hot showers, laundry, and lots of exterior doors or windows all add moisture to the air. The calculator bumps the capacity up so your unit doesn’t constantly run at full blast.

5. Read the recommendation and size category.
   The result shows a target pints/day rating and a simple category like “small room,” “medium room,” or “basement/high-capacity”. Use that as your target when you look at real models.

This isn’t meant to replace manufacturer sizing charts, but it gives you a much better starting point than guessing between a 20-pint and a 50-pint unit.

What does “pints per day” mean on a dehumidifier?

When you see dehumidifiers advertised as 20-pint, 35-pint, 50-pint, 60-pint, etc., that number is the nameplate capacity:

• It’s how many pints of water the unit can remove from the air in 24 hours under standardized test conditions.

• It’s not a guarantee of what it will pull out in your exact basement or bedroom, but it lets you compare models on the same scale.

So if the calculator recommends 40 pints/day, that doesn’t mean you’ll actually collect exactly 40 pints of water every single day. It means:

“Look for a dehumidifier whose rating is in the ~40-pint class, not a tiny 20-pint unit.”

In real life, what you actually see in the bucket depends on room temperature, how wet the space is, how often the compressor cycles, and how long you run it.

Small Room Dehumidifier

Mid-Size Dehumidifier

Large Space Dehumidifier

Click the Box That Fits Your Needs to Browse The DIY Team's Dehumidifier Reccomendations on Amazon

Example dehumidifier sizing scenarios

Here are a few “real world” examples that match what the calculator would output:

• Small bedroom – slightly damp

  • ~150 ft² bedroom, upstairs, standard climate

  • Feels a little sticky in the summer but no visible condensation

  • 1–2 people sleeping there
    → The calculator will usually land in the 20–25 pint range (small room dehumidifier).

• Medium living room – moderately damp

  • ~300–400 ft² living room on the main floor

  • Occasional musty smell, especially after rain

  • 3–4 people using the space regularly, several windows
    → Expect a recommendation around 30–40 pints/day (medium room dehumidifier).

• Large basement – very damp / humid

  • ~700–900 ft² unfinished basement

  • Musty smell most of the time, some visible damp spots on walls

  • Humid or coastal climate, laundry area in the same space
    → The calculator will often suggest 45–60 pints/day or higher (basement / high-capacity unit), sometimes pushing into the 70-pint class if conditions are bad enough.

These examples show why a one-size-fits-all “just buy a 30-pint unit” rule doesn’t really work. Floor area, dampness, and climate all matter.

Is it better to oversize or undersize a dehumidifier?

If you have to choose, it’s usually safer to be slightly oversized rather than undersized:

• A too-small dehumidifier may run constantly, never quite getting the humidity under control. That wastes energy and still leaves the room feeling damp.

• A slightly larger unit can pull moisture out of the air faster, then cycle off or run on a lower fan setting. That can actually be quieter and more efficient in a very damp room.

That said, there’s no need to jump from a 30-pint recommendation straight to the biggest 70-pint monster you can find. A modest step up (for example, using a 35–40 pint unit when the calculator suggests 30) is usually enough margin for most homes.

When might you need more than one dehumidifier?

One unit is usually enough for a single, open space. But you might consider more than one dehumidifier if:

• Your basement has multiple separate rooms with doors closed most of the time.

• You have two floors that both stay very humid (for example, a damp basement and a stuffy upstairs).

• You’re dealing with very large square footage that pushes well beyond the upper end of standard portable units.

In those cases, it can be more practical to use two correctly sized units rather than trying to force one dehumidifier in a corner to handle the whole house.

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