Pick the right dehumidifier pint capacity for your room size.
Dehumidifiers are rated in pints of water removed per day, and the AHAM reference point is 20 pints for a 500 sq ft moderately damp space at an 8 ft ceiling. Scale that by your actual area and ceiling height, multiply by a dampness factor for how wet the space really is, and add a couple of pints per occupant beyond two, because people and their laundry are significant moisture sources. Then round up to a stock capacity. Two things trip people up: capacity ratings changed in 2019 to a cooler test condition, so a modern 20 pint unit is roughly the old 30 pint model, and no dehumidifier fixes a leak — if the walls are seeping, the machine is managing a symptom.
Dehumidifier Size
Base pints = (area / 500) x 20 x (ceiling height / 8); required = base x dampness factor + 2 pints per occupant above two; round up to a stock capacity
The DOE test condition changed in 2019 from 80 F to 65 F, which lowers the measured output. A current 20 pint unit is broadly the same machine as a pre-2019 30 pint one.
45-50% relative humidity. Below 40% is unnecessary and wastes energy; above 60% supports mould and dust mites.
It controls the air, not the cause. If water is entering through the wall or slab you need drainage, grading or sealing work — the dehumidifier just stops the resulting humidity from damaging contents.