Basements often feel more humid than the rest of the house. They stay cooler, sit against soil, and usually have less airflow. That changes how you size a dehumidifier.
For the full sizing framework, start with How Big of a Dehumidifier Do I Need for My Home?
Why Basements Run Damp
Basements typically:
- Stay cooler than upper floors
- Have concrete walls that transmit moisture
- Experience limited air circulation
Cooler air raises relative humidity even when total moisture is moderate. If you have not measured your humidity yet, read How Do I Measure Relative Humidity (RH) in My House?
Typical Basement Size Guidance
In most homes:
- Under 800–1000 sq ft with moderate humidity
→ Small: 30–40 pint - Around 1000–1500 sq ft
→ Medium: 40–50 pint - Large, consistently damp, or musty basements
→ Large: 50–70 pint
If humidity regularly stays above 60%, moving up one size class is generally more effective than running a smaller unit constantly.
Related Reading
Practical Recommendation
For most unfinished basements between 900–1400 sq ft with typical moisture levels, a 40–50 pint unit is usually a balanced starting point. If humidity remains high after several weeks of operation, stepping up to 50–70 pints often improves stability. When in doubt, slightly larger units generally perform more steadily than undersized overworked ones.
Portable Dehumidifier Size Options
Small Dehumidifiers (30–40 pint)
Medium Dehumidifiers (40–50 pint)
Large Dehumidifiers (50–70 pint)
Conclusion
Basement sizing depends more on moisture conditions than square footage alone. Slightly oversizing is generally safer than undersizing. For the complete sizing logic, return to How Big of a Dehumidifier Do I Need for My Home?