What size dehumidifier do I need? Start with moisture load

Start with what you can observe

Write down the room, temperature, humidity reading, moisture source, and when the problem is worst. A single reading is less useful than a pattern. Compare mornings with evenings and dry weather with rain. Keep the hygrometer away from direct appliance exhaust, windows, and shower spray.

Choose the water route before the machine

Gravity drainage needs a hose that slopes continuously downward to a lower drain. A built-in pump can lift water, but adds complexity and still has height and routing limits. Bucket operation is flexible but transfers the work to a person; estimate the filled weight and the path to the sink.

Know what a dehumidifier cannot fix

A portable unit manages water vapor. It does not repair roof leaks, foundation seepage, plumbing failures, missing bathroom ventilation, or unsafe electrical placement. Stop and address bulk water first. For recurring mold, health concerns, or building damage, use qualified local professionals.

Set up for airflow and safety

Use a level surface, the clearances in the exact manual, a suitable grounded receptacle, and a closed-room test period. Clean the filter on schedule. Do not use extension cords unless the manufacturer explicitly permits them, and keep the appliance outside splash zones.