Dehumidifier Size Calculator
Dehumidifier pints per day for your room size and dampness.
About this tool
Enter the area in square feet or square metres and choose how damp the space is. The tool gives the recommended capacity from the traditional AHAM chart, in pints and litres per day, the equivalent post-2019 DOE rating, and a common size to look for.
Sizing a dehumidifier
Dehumidifiers are rated by how much water they can remove per day. The traditional AHAM sizing chart matches capacity to floor area and dampness. A moderately damp space (musty in humid weather) needs about 10 pints a day for 500 sq ft and 14 for 1,000 sq ft. Very damp spaces (always musty, damp patches) need 12 and 17. Wet spaces (sweating walls) need 14 and 20, and extremely wet ones (standing water) 16 and 23, rising by roughly 4โ7 pints per extra 500 sq ft. In 2019 the US Department of Energy changed its test to cooler, more realistic conditions, so the same machine now has a lower rating: an old '70-pint' model is sold as about 50 pints. The tool shows both. Choose the next size up for basements, laundry rooms, high ceilings, big households or homes with tumble dryers. Aim for 40โ50% relative humidity, checked with an inexpensive hygrometer. Honest limits: charts are a starting point. Fix leaks, gutters and ventilation first, and for cold garages or basements choose a model rated for low temperatures or a desiccant type. The dew point calculator and the CFM calculator are related.
Frequently asked questions
What size dehumidifier do I need for a basement?
For a 1,000 sq ft very damp basement, about 17 pints a day on the old scale, around 12 pints on 2019 ratings; size up if in doubt.
Why are dehumidifier pint ratings lower now?
Since 2019 the US DOE tests at 65 ยฐF instead of 80 ยฐF, so the same unit gets a lower pint rating.
What humidity should I aim for?
About 40 to 50% relative humidity indoors.
How many litres is a pint?
A US pint is 0.473 litres, so 30 pints a day is about 14 litres.
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.