What size dehumidifier do I need for a basement?

Find the floor area and the dampness tier in the table. Under 2,000 square feet, a slightly to moderately damp basement takes 20 to 30 pints per day, a very damp one 25 to 40, and a wet one 30 to 50. Over 2,000 square feet the cells read 30+, 40+ and 50+.

Is it better to oversize or undersize a dehumidifier?

Oversize. Unlike an air conditioner, a larger dehumidifier does not short-cycle into a comfort problem. It reaches the target humidity faster, runs fewer hours, and keeps capacity in reserve. This calculator therefore rounds toward the larger size.

Why does a 35-pint unit today look like an old 60-pint model?

Because the test temperature changed. Portable dehumidifiers are now rated at 65 degrees Fahrenheit rather than 80, so the same machine carries a smaller honest number. Always compare two units on the same rating basis.

How do I tell whether a space is damp, very damp, or wet?

Use the table's own descriptions, which are the options in the calculator: an intermittent musty odour is slightly to moderately damp, 50 to 75 percent relative humidity; a space that consistently smells damp with damp spots on walls or floors is very damp, 75 to 90 percent; sweating walls or visible seepage is wet, 90 to 100 percent. A cheap hygrometer settles it directly.

Does this work as a dehumidifier size chart for a whole house?

No, and it should not be used as one. A whole-house or crawlspace job needs a load calculation and a ducted unit; this chart is a room-scale chart, and the page says so instead of extrapolating past its published range.

Dehumidifier calculator

Enter the floor area and how damp the space is. You get the published capacity band for that cell, and one suggested size — with the cell named. If you came looking for a dehumidifier size calculator, this is the same instrument: one page covers the whole question.

Reference Goods Review Lab Last updated 10 October 2026 Capacity bands from the published ENERGY STAR sizing table, on the current DOE rating basis

How do you want to give the area?

Floor area Length × width

Floor area

ft²

Length × width

× ft

Floor area 1,200 ft²

Ceiling height optional

Used for the note below the result. The published table is by floor area.

How damp is the space, before any dehumidifier?

Slightly to moderately damp 50–75% RH Feels damp, with a musty odour that may come and go. Very damp 75–90% RH Consistently feels and smells damp; damp spots appear on walls or floors. Wet 90–100% RH Walls or floor sweat, or seepage is present; heavy loads such as laundry drying. Extremely wet standing water Sopping surfaces or standing water. Uses the same published cell as Wet — the table stops there.

Suggested size

— pints/day

Published range for this cell: —

Cell used: —
Area band: —
Basis: ENERGY STAR sizing table, current DOE rating basis

In short

What this does: Looks your space up in the published ENERGY STAR dehumidifier sizing table — the AHAM-derived chart — and returns the capacity band for that cell, plus one suggested size.
What decides the answer: Two things: the floor area, split at 2,000 ft², and how damp the space is without a dehumidifier, in three published tiers.
Which size it suggests: The top of the published range for a small–medium room, and the published minimum for the open-ended large-room cells — because the published advice is that it is better to oversize than undersize.
The part most pages leave out: Every number here is on the current DOE rating basis. The test temperature changed in 2019, so a unit once sold as 60 pints is roughly a 35-pint machine today. Two charts can disagree and both be honest.

How this calculator picks a number

It does not run a formula. It looks up a published cell. The capacity bands below are the ones on the ENERGY STAR dehumidifier buying guidance sizing table — the industry-standard chart derived from AHAM's sizing guidance — split by floor area and by how damp the space is without a dehumidifier. The same table is what most pages reproduce as a dehumidifier size chart; here it is the thing doing the work, rather than a picture you have to read off by eye.

Published capacity bands, in pints per day, on the current DOE rating basis
Dampness of the space	Under 2,000 ft²	2,000 ft² and over
Slightly to moderately damp	20–30	30+
Very damp	25–40	40+
Wet	30–50	50+

Two decisions follow from the table, and both are stated here rather than hidden inside the arithmetic. The band boundary is 2,000 ft², and a space of exactly that size counts in the larger band. The suggested size follows the published advice, which is ENERGY STAR's own wording: it is better to oversize than undersize. Our rounding rule applies it — the top of the range for the smaller band, and the published minimum for the open-ended larger cells, where the table stops giving an upper bound. A larger unit reaches the target humidity faster, runs fewer hours, and has reserve for laundry days and wet spells, while an undersized one runs continuously and never catches up.

The number on the label changed in 2019

This is the part most sizing pages leave out, and it is the reason two charts can disagree while both are honest. The US Department of Energy's test procedure for portable dehumidifiers now runs them at 65 °F instead of 80 °F, to match real basement conditions where a compressor extracts less water. The hardware did not change; the rating did. A unit once sold as a 60-pint machine is roughly a 35-pint machine on the current basis.

So when you compare a listing against an old chart, compare like with like. Listings often print both — something like “50 pint (previously 70 pint)”. Every number on this page is on the current basis. The underlying test procedure is 10 CFR 430 Appendix X1.

What this table does not cover

The chart is for a portable unit in a room-scale space. Two cases sit outside it, and this calculator says so rather than stretching the table to reach them:

A whole house, or a sealed crawlspace. Those call for a ducted whole-home dehumidifier sized from a moisture-load calculation, not a portable unit sized from a room chart.
A space far outside the area bands. Above the table's range the published cells are open-ended (“50+”), so the table stops being a sizing instrument and becomes a floor.

One more caveat worth stating plainly: a room can be damp for a reason no dehumidifier fixes. If water is entering through a wall or a floor, the machine will run continuously and lose. Sizing is the second question; the first is where the water comes from.

Questions this page answers

What size dehumidifier do I need for a basement?: Find the floor area and the dampness tier in the table. Under 2,000 square feet, a slightly to moderately damp basement takes 20 to 30 pints per day, a very damp one 25 to 40, and a wet one 30 to 50. Over 2,000 square feet the cells read 30+, 40+ and 50+.
Is it better to oversize or undersize a dehumidifier?: Oversize. Unlike an air conditioner, a larger dehumidifier does not short-cycle into a comfort problem. It reaches the target humidity faster, runs fewer hours, and keeps capacity in reserve. This calculator therefore rounds toward the larger size.
Why does a 35-pint unit today look like an old 60-pint model?: Because the test temperature changed. Portable dehumidifiers are now rated at 65 degrees Fahrenheit rather than 80, so the same machine carries a smaller honest number. Always compare two units on the same rating basis.
How do I tell whether a space is damp, very damp, or wet?: Use the table's own descriptions, which are the options in the calculator: an intermittent musty odour is slightly to moderately damp, 50 to 75 percent relative humidity; a space that consistently smells damp with damp spots on walls or floors is very damp, 75 to 90 percent; sweating walls or visible seepage is wet, 90 to 100 percent. A cheap hygrometer settles it directly.
Does this work as a dehumidifier size chart for a whole house?: No, and it should not be used as one. A whole-house or crawlspace job needs a load calculation and a ducted unit; this chart is a room-scale chart, and the page says so instead of extrapolating past its published range.

Where these numbers come from

The capacity bands and the three dampness descriptions are the published ENERGY STAR dehumidifier sizing table's, which is itself the AHAM-derived chart. The 65 °F test change and the old-to-new pint conversion come from the same programme's guidance on dehumidifier testing and capacity, and the procedure behind the current ratings is 10 CFR 430 Appendix X1. Nothing on this page is a test result, and no number here was estimated.