When I first started wondering what size dehumidifier for basement would be ideal, I had no idea how complicated the choice could be. I assumed I could just pick any dehumidifier from a store shelf, plug it in, and my damp, musty basement would magically turn fresh and dry. But after living with a persistent basement humidity problem—and trying out more than one dehumidifier—I learned that size matters more than most people realize. In this guide, I’ll walk you through my experience figuring out the right size dehumidifier for a basement, step by step, and help you make the best choice for your space.
Step 1: Understand Why Size Matters
Before buying my first dehumidifier, I didn’t think size was all that important. But the truth is, getting the wrong size can make your dehumidifier almost useless. My first unit was a small, 20-pint dehumidifier. It worked fine for a closet, but for my 900-square-foot basement, it barely made a difference. The air still felt damp, and the musty smell never went away.
That’s when I learned that dehumidifiers are rated based on how much moisture they can remove in 24 hours. If you choose one that’s too small, it will run constantly, overwork itself, and fail to bring the humidity down to safe levels (ideally 45–50%). On the other hand, buying one that’s too large isn’t necessarily a bad thing—it might cycle less often but will pull out moisture more quickly.
Step 2: Measure Your Basement
The next thing I did was measure my basement. It sounds obvious, but many people don’t bother to do this. Mine was roughly 30 feet by 30 feet, which equals about 900 square feet. Why does this matter? Because dehumidifier manufacturers use square footage as a baseline for recommending sizes.
But size alone isn’t enough. You also need to consider how damp your basement is. A lightly damp basement will need a smaller unit compared to one that feels wet and has visible condensation on walls or pipes.
Step 3: Learn the Sizing Guidelines
After some research (and trial and error), I discovered the general sizing rules most experts recommend:
For small basements (500–1,000 sq. ft.) with mild dampness: A 30–40 pint dehumidifier usually works.
For medium basements (1,000–2,000 sq. ft.) or moderate dampness: You’ll need a 50-pint model.
For large basements (2,000+ sq. ft.) or very wet conditions: Go for a 70-pint or higher unit.
When I switched from my 20-pint model to a 50-pint one, the difference was night and day. Within a few days, the air felt drier, and the musty smell was almost gone. This was my first real win in the battle against basement humidity.
Step 4: Assess the Moisture Level
Even if you know your basement’s size, you also need to think about how damp it is. My basement had some water seepage after heavy rains, which meant my humidity was always high. If your basement feels just slightly damp, a mid-range unit will do. But if you have visible water stains or it smells musty all the time, go bigger.
To make this easier, I bought a hygrometer—an inexpensive device that measures humidity. This helped me track how much moisture I was dealing with and whether the dehumidifier was actually working.
Step 5: Consider Features That Make a Difference
When figuring out what size dehumidifier for basement I needed, I also learned that features matter as much as size. My first unit didn’t have an auto-drain, which meant I had to empty the bucket every few hours. My 50-pint unit, on the other hand, came with a pump for continuous drainage—an absolute game-changer.
Other features I found helpful:
Humidistat: Lets you set a target humidity level so the machine shuts off when it’s achieved.
Auto-restart: Restarts automatically after a power outage.
Defrost function: Prevents coil freezing in cold basements.
If you’re investing in a larger unit, these features make day-to-day use much easier.
Step 6: Compare Real-World Performance
I ended up testing two different dehumidifiers—a 35-pint and a 50-pint—in the same space. The 35-pint unit ran almost constantly but never got my humidity below 55%. When I upgraded to the 50-pint model, it reached 45% within a few days and cycled on and off instead of running nonstop.
This experience taught me that sometimes going a size bigger than you think you need can save you energy and frustration in the long run.
Step 7: Calculate Cost vs. Benefit
Yes, larger dehumidifiers cost more upfront. But here’s what I realized: a smaller unit that can’t keep up will run 24/7, wasting electricity and still not solving the problem. My 50-pint unit may have been more expensive initially, but it ended up being more efficient—and it protected my basement from mold, which can be far more costly to fix.
Final Thoughts: What Size Dehumidifier for Basement Is Right for You?
So, what size dehumidifier for basement do you really need? It boils down to three things: the size of your basement, how damp it is, and whether you want extra features that make maintenance easier. If your basement is under 1,000 square feet and only slightly damp, a 30–40 pint model will likely do the job. But if it’s larger or has significant moisture problems, I strongly recommend going for at least a 50–70 pint model.
From my personal experience, erring on the side of a bigger unit is worth it. It works faster, requires less babysitting, and gives you peace of mind knowing your basement stays dry and mold-free.