A crawl-space dehumidifier should be sized for the space, moisture load, air leakage, drainage condition, and whether the crawl space is sealed. A unit that is too small can run constantly without controlling humidity. A unit that is oversized for the wrong problem can hide water issues without fixing them.
Use this calculator to estimate a practical dehumidifier size range before buying equipment or comparing contractor recommendations. This is a planning tool, not an equipment specification.
Estimate your crawl-space dehumidifier size
How this sizing estimate works
The calculator starts with crawl-space area, then adjusts the estimated dehumidifier size for height, moisture condition, sealing, vapor barrier quality, drainage, climate humidity, and air movement.
When a dehumidifier is not the first fix
A dehumidifier can help control humidity after the water source is controlled. It should not be used as the main fix for standing water, repeated water entry, missing drainage, open vents, or a torn vapor barrier.
What changes the size most
- Crawl-space size and height
- Whether the space is sealed or vented
- Whether the ground vapor barrier is complete
- Whether water appears after rain
- Whether the space has standing water
- Humidity level in the climate
- Whether air can move through the whole crawl space
Do not buy by pint rating alone
Two dehumidifiers with similar pint ratings may perform differently depending on temperature, airflow, ducting, drainage, and how the manufacturer rates the unit. A sealed, drained crawl space usually needs a different approach than a vented, wet crawl space.