Dehumidifier Size Calculator

This dehumidifier size calculator tells you how many pints of moisture per day your dehumidifier should remove. Enter the floor area of the basement or room and pick how damp it is without a dehumidifier, from moderately damp to extremely wet. The result comes from the AHAM sizing chart that ENERGY STAR references.

You can work in square feet and pints or switch to square meters and liters. One catch matters when you shop: the chart uses the older pint ratings. Since 2019, the Department of Energy test gives lower numbers for the same machine, so the calculator also shows a rough equivalent on the newer scale.

How to Use the Dehumidifier Size Calculator

1
Pick your units
Choose US (sq ft, pints) or Metric (m², liters). Switching converts any area you have already entered.
2
Enter the area
Type the floor area of the open space the dehumidifier will serve, such as the whole basement, between 50 and 10,000 sq ft.
3
Choose the dampness condition
Select moderately damp, very damp, wet or extremely wet. A short description under the menu helps you choose.
4
Read the capacity
See the recommended pints or liters per day on the older AHAM scale, plus the rough equivalent on newer post-2019 labels. Your condition is highlighted in the chart below.

How the dehumidifier sizing works

The Association of Home Appliance Manufacturers (AHAM) chart lists the pints of water per day a dehumidifier should remove for spaces from 500 to 2,500 sq ft in four dampness conditions. The chart rises by a fixed number of pints for each extra 500 sq ft, so the calculator fills in sizes between the rows on a straight line and rounds up to a whole pint.

Spaces smaller than 500 sq ft use the 500 sq ft row. Above 2,500 sq ft, the chart stops and the calculator extends it at the same rate, flagged as an estimate.

Pints per day = base + step x (area in sq ft - 500) / 500, rounded up. Moderately damp: base 10, step 4. Very damp: base 12, step 5. Wet: base 14, step 6. Extremely wet: base 16, step 7.

AHAM dehumidifier sizing chart

Pints per day under the older test, by area and condition without a dehumidifier running.

Moderately damp: feels damp and smells musty only in humid weather
Very damp: always feels damp and smells musty; damp spots on walls or floor
Wet: feels and smells wet; walls or floor sweat, or water seeps in
Extremely wet: laundry drying in the space, wet floor, or other heavy moisture loads

Area	Moderately damp	Very damp	Wet	Extremely wet
500 sq ft	10	12	14	16
1,000 sq ft	14	17	20	23
1,500 sq ft	18	22	26	30
2,000 sq ft	22	27	32	37
2,500 sq ft	26	32	38	44

The 2019 rating change: old pints vs new pints

In 2019 the Department of Energy changed the dehumidifier test from 80°F to 65°F at 60% relative humidity, closer to real basement conditions. Cooler air holds less water, so the same machine now earns a lower pint rating. A unit once sold as 70 pints is typically labeled about 50 pints today, and an old 50-pint unit about 35 pints.

The AHAM chart predates the change, so its numbers are on the old scale. The calculator shows a rough new-scale equivalent at about 70% of the old figure. If a product lists both ratings, compare the chart result to the old one.

Worked example: a 1,200 sq ft basement

Your basement is 30 ft by 40 ft, or 1,200 sq ft, and the walls sweat in summer, so you choose Wet.

Wet row: base 14 pints, plus 6 pints per extra 500 sq ft
14 + 6 x (1,200 - 500) / 500 = 14 + 8.4 = 22.4 pints per day
Rounded up: 23 pints per day on the older AHAM scale, about 10.9 liters per day
On a new (post-2019) label, look for roughly 16 pints or more

Tips for getting the most from a dehumidifier

When unsure between two conditions, choose the wetter one. A slightly larger unit runs less and handles humid spells better.
Aim for indoor humidity below 60%, and ideally between 30% and 50%. A cheap hygrometer tells you whether the unit is keeping up.
Fix water sources first. Gutters, downspouts, grading and plumbing leaks cause dampness that no dehumidifier will cure.
Close windows and doors to the space so the unit is not drying outdoor air.
Use a floor drain or condensate pump for continuous drainage in basements so the bucket never stops the unit.
Standing water, active leaks or mold growth call for a waterproofing or remediation professional, not just a larger dehumidifier.

Features

AHAM sizing chart for moderately damp, very damp, wet and extremely wet spaces
Area in square feet or square meters
Capacity in pints per day or liters per day
Rough conversion to the lower ratings used since the 2019 DOE test change
Full sizing chart shown with your condition highlighted

Frequently Asked Questions

What size dehumidifier do I need for 1,000 square feet?

On the AHAM chart, 1,000 sq ft needs 14 pints per day if moderately damp, 17 if very damp, 20 if wet and 23 if extremely wet. Those are older pint ratings. On a dehumidifier tested under the 2019 procedure, the roughly equivalent ratings are about 10, 12, 14 and 16 pints, so the smallest current models, often around 20 pints, usually cover it.

What size dehumidifier do I need for a basement?

Measure the basement floor area and judge how damp it gets. A 1,500 sq ft basement that always smells musty is very damp and needs about 22 pints per day on the AHAM chart. If the walls sweat or water seeps in, choose wet, which gives 26 pints. Basements often run damper than they seem, so rounding up to the next condition is sensible.

Why do new dehumidifiers have lower pint ratings?

Since 2019, the Department of Energy tests dehumidifiers at 65°F instead of 80°F, both at 60% relative humidity. Cooler air carries less moisture, so a machine removes less water in the test and gets a lower rating. Capacity did not really shrink. A unit once rated 70 pints is now typically rated about 50 pints, and an old 50-pint unit about 35.

Is it bad to buy a dehumidifier that is too big?

Usually not. A larger dehumidifier reaches the target humidity faster, then cycles off, and it copes better with very humid weeks. The main downsides are a higher purchase price, more floor space and, for some models, more noise. A unit far too small is the bigger problem, because it runs constantly and may never bring humidity down to a healthy level.

What humidity level should a basement be?

Keep basement humidity below 60% to discourage mold and dust mites, and ideally between 30% and 50%. Set the dehumidifier to around 45 to 50% and check with a separate hygrometer. If the unit cannot hold that level even when running continuously, it is undersized, or there is a water problem that needs fixing at the source.

How many liters per day is a 50 pint dehumidifier?

One US pint is about 0.473 liters, so 50 pints per day is about 23.7 liters per day. Keep in mind which test the rating uses. A 50-pint rating under the older test is roughly a 35-pint rating under the 2019 test, about 16.6 liters per day. Switch the calculator to metric to see results in liters.

Last reviewed September 21, 2026