Free dehumidifier tool

Exactly the right dehumidifier size. In 10 seconds.

Enter your square footage, humidity, and room type. Get the pint capacity you actually need, not what the big-box label upsells you. Free, no signup.

AHAM 2019 + DOE 2020 No affiliate bias Free PDF export

Four factors visualized for the dehumidifier size calculator tool — Four inputs drive every sizing read: room size, current humidity, airflow, and the capacity you need.

Enter your room. See your size instantly.

Square footage 500 sq ft

Floor area of the space you want to dry. Measure length × width. Whole home = add all conditioned rooms.

Current humidity 65%

Read from a $15 hygrometer or smart thermostat. 50% is comfortable, 60%+ is mold-risk, 70%+ is wet.

Room type

Sized for your space

30-50

Pint capacity range (pints per day)

Move a slider to see your exact size.

Heads up: Sizing guidance based on AHAM 2019 residential dehumidifier capacity tables and DOE 2020 integrated energy factor standards. Actual pint capacity depends on temperature, leak load, and outdoor intrusion. Not a medical, structural, or legal diagnosis. If you see active mold, bring in a licensed inspector.

Typical coverage by capacity

What each standard pint-capacity tier handles, based on AHAM 2019 coverage tables at 60 percent relative humidity. Assume moderately damp conditions. Higher humidity or colder rooms push you up a tier.

Capacity	Dry room	Damp room	Wet room	Best for
20 pint	up to 500 sq ft	up to 300 sq ft	not rated	small bedroom, closet
30 pint	up to 1,500 sq ft	up to 800 sq ft	up to 500 sq ft	bedroom, small living room
50 pint	up to 2,500 sq ft	up to 1,500 sq ft	up to 1,000 sq ft	basement, damp first floor
70 pint	up to 4,500 sq ft	up to 2,500 sq ft	up to 1,500 sq ft	wet basement, whole home

Dry: 50-60% RH, no damp smell. Damp: 60-70% RH, musty when closed up. Wet: 70%+ RH, visible dampness, standing water possible. Source: AHAM ANSI/AHAM DH-1-2019 coverage standard.

Why this range? (the AHAM chart, explained)+

AHAM 2019: The Association of Home Appliance Manufacturers sets the residential sizing standard. The chart maps square footage × humidity condition (dry, damp, wet) to a pints-per-day capacity. This calculator uses that chart, then adjusts for room type.

Room-type multiplier: Basements get 1.2x because cold exterior walls and slab flooring add condensation load. Crawl spaces get 1.3x because they are unconditioned and sit in ground moisture. Bathrooms get 0.9x because they are usually smaller and better ventilated than the nominal sqft suggests.

DOE 2020 energy factor: Newer units have lower pint ratings on the label because the DOE changed the test condition from 80F/60%RH to 65F/60%RH. A 2019 70-pint unit is roughly a 2020 50-pint unit. Same hardware, different sticker. Our tool outputs the 2020 (IEF) rating.

When to size up: If temperature is below 65F, if the space has active water intrusion, or if you need 40-45% RH (archival storage), jump to the next tier.

How it works

Tell us the room

Square footage, current humidity, and room type. That is it.

We run AHAM 2019

The same sizing formula home inspectors and HVAC techs use on every job.

Get the pint range

A low-mid-high capacity range and a neutral tier comparison. No brand pushing.

FAQ

What is AHAM 2019 sizing?

AHAM 2019 (ANSI/AHAM DH-1-2019) is the residential dehumidifier capacity standard. It maps square footage against humidity condition (dry 50-60%, damp 60-70%, wet 70%+) to a recommended pints-per-day rating. Every reputable retailer uses this chart. The DOE 2020 integrated energy factor (IEF) rule changed the pint-rating test conditions, so 2020+ units post smaller numbers on the label for the same real-world performance. This calculator returns 2020 IEF pint ratings.

Do I need a dehumidifier for my basement?

If your basement runs above 60 percent humidity for more than a few days a year, yes. Sustained humidity above 60 percent lets common mold species (Aspergillus, Cladosporium, Penicillium) colonize porous surfaces within 3 to 7 days. Basements are 1.2x more load than a same-sqft bedroom because cold slab floors and exterior walls condense water first. Target 45 to 55 percent RH year-round.

How long should a dehumidifier run?

A correctly sized unit runs 60 to 80 percent of the time in humid months and 20 to 40 percent in winter. If your unit runs 100 percent of the time, it is undersized. If it rarely kicks on and humidity is still high, your hygrostat is broken or misplaced. Most modern units let you set a target humidity; 50 percent is the safe-mold comfort sweet spot.

Does a higher-capacity dehumidifier save energy?

Usually yes. A 50-pint unit running at 40 percent duty cycle typically uses less electricity than a 30-pint unit running at 90 percent duty cycle to hit the same target. Look for ENERGY STAR certified units with an Integrated Energy Factor (IEF) of 1.8 L/kWh or higher. Oversizing by one tier is almost always a win for both comfort and energy. Don't go more than one tier above the calculator's recommendation, or short cycling will hurt efficiency and wear the compressor faster.