Dehumidifier Size Calculator (Pints/Day)

It depends on dampness. For a very damp 1,000 sq ft room the AHAM chart gives 12 + 5 × (1000/500 − 1) = 17 pints per day, so you round up to the nearest retail size: a 20-pint unit (AHAM rating). That same unit is labeled about 14.3 pints under the DOE 2019 rating, which is the number printed on the box. A merely moderately damp room that size needs only 14 pints per day, still a 20-pint unit.

The Association of Home Appliance Manufacturers (AHAM) chart lists pints of water removed per 24 hours by room size and dampness. Per 500 sq ft the bases are: moderately damp 10, very damp 12, wet 14, extremely wet 16 pints. Add 4, 5, 6, or 7 pints respectively for each additional 500 sq ft. So a wet 1,500 sq ft space needs 14 + 6 × 2 = 26 pints per day. These pints use the older 80°F/60% RH test conditions.

In 2019 the DOE changed the rating test from 80°F/60% RH to 65°F/60% RH, and ENERGY STAR required new labels. Rated capacity fell about 29%: a unit rated 70 pints under the old test is sold as 50 pints under DOE 2019, a ratio of 50/70 ≈ 0.714. This calculator sizes in AHAM pints and converts, so the recommendation matches the number on the box.

A typical 50-pint unit draws about 500 W. Running 8 hours a day at $0.17 per kWh uses 4.0 kWh per day, costing $0.68 per day — about $20.40 per month. Larger or older units draw more; the assumptions panel lets you enter your actual wattage, hours, and electricity rate.

Yes. Basements and crawl spaces sit against cool earth and seep moisture, so add about 10% capacity (typical range 10–15%). Example: an 800 sq ft wet room needs 14 + 6 × (800/500 − 1) = 17.6 pints per day; as a basement that becomes 17.6 × 1.10 = 19.36 pints, rounded up to a 20-pint unit.

Below about 60°F a standard compressor dehumidifier loses efficiency noticeably — choose a low-temperature auto-defrost model. Below about 50°F the coils ice up and a compressor unit removes almost nothing; use a desiccant or low-grain-refrigerant (LGR) dehumidifier rated for cold operation instead.

Yes, for ceilings above the 8 ft reference: scale capacity by ceiling height ÷ 8. Example: a 600 sq ft moderately damp room needs 10 + 4 × (600/500 − 1) = 10.8 pints per day; with a 10 ft ceiling that becomes 10.8 × 1.25 = 13.5 pints, so a 20-pint unit still covers it.

Only if air moves freely between them (open plan, no closed doors). Otherwise each room needs its own sizing, because a closed door starves the second room of airflow. Use compare mode above: it sizes each room and also shows the single-unit size for the combined area at the worse dampness level.