Is 20 pints enough for a basement?

It is the bottom of the first cell, not a recommendation. The published band for a space under 2,000 square feet that is slightly to moderately damp is 20 to 30 pints a day, so 20 is the floor of that band. Read the top of the band you land in rather than the bottom, and pick the band by the worst month rather than an average afternoon.

What is the difference between a 50-pint dehumidifier and a 50-pint tank?

One is a rate and the other is an amount. The capacity figure is pints of water removed per 24 hours under specified ambient conditions; the tank figure is pints of water the tank holds before it needs emptying. Both are printed in pints on the same product page, and only the first one is the number the sizing chart speaks in.

How many pints are in a gallon?

Eight US pints to a US gallon. That is why the capacity figure scales quickly: a 50-pint day is 6.25 US gallons of water in 24 hours, and no tank measured in the same pints holds a day of it.

What is the best dehumidifier for a basement right now?

There is no single best, because the answer is a cell rather than a model. The machine that fits a basement is the one whose capacity sits in the published cell for that basement's floor area band and dampness, at the temperature the space actually runs. A ranking that does not name your cell is answering a different question, and one that is quoted on the older 80 degree rating basis is quoting a different quantity.

Does a cold basement change how many pints I need?

It changes whether any figure applies. Capacity is normalised to 65 degrees Fahrenheit dry-bulb and 60 percent relative humidity for a portable unit, while the same test procedure notes units may encounter 55 to 80 degrees in service. A room below the rating condition gets less than the label, and below roughly 65 degrees the condensing coil can frost, which is a different machine rather than a bigger number.

How many pints dehumidifier do I need?

The answer is a rate, not an amount. The published chart gives it in pints per day; the same product page also prints pints for the tank, and those two numbers are not the same kind of thing. Here is the cell you are looking for, what the figure is measured at, and why the tank is the spec that decides whether you can leave the machine alone.

Research review Goods Review Lab Last updated 14 October 2026 Capacity cells from the published ENERGY STAR sizing table; the pint definition, the 65 °F test condition and the service temperature range from the US Department of Energy test procedure

In short

The number you are looking for: Capacity in pints per day, read off the published chart by floor area and by how damp the space is. Under 2,000 ft² the cells are 20–30, 25–40 or 30–50. Over 2,000 ft² they read 30+, 40+ and 50+.
Why “pints” is two questions: On the capacity spec, pints means pints of water removed per day — a rate. On the tank, pints means pints of water the tank holds — an amount. A unit rated 50 pints a day against a tank that holds 20 pints is a tank emptied every nine and a half hours. The division is ours; the 24-hour basis is the test procedure’s.
What the rating is taken at: The test procedure defines capacity as the pints collected per 24 hours of operation under specified ambient conditions, and for a portable unit that condition is 65 °F dry-bulb and 60% relative humidity. The same document notes that units may meet anything from 55 °F to 80 °F depending on where they are installed.
Which way to round: Read the top of the band you land in, not the bottom — and pick the band by the worst month, not by how the room feels on an average afternoon.

The two pints on the same page

Search for how many pints you need and you will be given a figure like “50 pints”. That figure has a definition, and it is worth having in front of you before you compare it with anything. The US Department of Energy’s test procedure states that product capacity for dehumidifiers is “a measure of the ability of the dehumidifier to remove moisture from its surrounding atmosphere, measured in pints collected per 24 hours of operation under the specified ambient conditions”.

So the spec number is a rate. It is how much water leaves the air in a day. It is not how much water the machine can hold. Those are two separate figures on the same product page, both printed in pints, and nothing on the page usually says that they are different quantities.

The tank is the second one, and it is the one that decides how the machine behaves in a week rather than on a datasheet. A tank is measured in pints too, but it is a volume sitting under the coil, not a rate. Put the two together and you get the number nobody prints:

tank empties per day = pints per day ÷ pints the tank holds

Work it through. Eight pints make a US gallon, so a 50-pint day is 6.25 US gallons of water in 24 hours. Against a tank that holds 20 pints, 50 ÷ 20 is two and a half fills a day, which is a tank emptied every nine and a half hours. Against a tank that holds 50 pints it is one fill a day. Both divisions are our arithmetic from the rating and the tank figure the product itself prints; the eight-pints-to-a-gallon conversion is the standard US one.

This is the part of the question that catches people, and it is not a sizing mistake. You can buy exactly the right capacity for the room, watch it pull the moisture out of the air precisely as promised, and still find yourself emptying a tank twice a day. The capacity was right. The tank was the part you never compared.

One product page, two pints

The capacity figure: A rate: pints of water removed per 24 hours, at a fixed test condition. This is the number the sizing chart speaks in, and the one to compare with the chart cell.
The tank figure: An amount: pints of water the tank holds before it needs emptying or the hose takes over. It does not change the capacity, and capacity does not change it.
Why they get confused: Both are printed in pints on the same page, in the same size type, next to each other. One is per day and the other is not, and the unit alone does not tell you which is which.
Which one to act on: Size from the rate; live with the amount. If the arithmetic above lands on more fills a day than you want to do, the fix is a drain hose or a pump, not a smaller machine.

The cell you are looking for

The rate comes off a published chart with two axes: a band of floor areas, and how damp the space is before you put anything in it. The three dampness descriptions and their humidity ranges are the chart’s own wording. The bands split once, at 2,000 square feet.

Published capacity bands, in pints per day, on the current rating basis
Condition of the space, without a dehumidifier	Relative humidity	Under 2,000 ft²	2,000 ft² and over
Slightly to moderately damp — feels damp, musty odour that may come and go	50–75%	20–30 pints/day	30 or more
Very damp — consistently smells damp, damp spots on walls or floor	75–90%	25–40 pints/day	40 or more
Wet — walls or floor sweat, or seepage is present	90–100%	30–50 pints/day	50 or more

If you would rather have the cell named for your own room than read it off a table, the dehumidifier calculator runs the same chart and shows which cell it used.

The three cells, in pints per day

The published cells for a space under 2,000 square feet. Each bar runs to the top of its band and the solid part marks the bottom, so the gap between them is the range the chart actually publishes rather than a single figure.

Under 2,000 ft² — the published cells

Slightly damp 20–30

Very damp 25–40

Wet 30–50

02550 pints per day

Three cells, and the top of the wettest one is 50 pints a day — which is the point at which the tank arithmetic above starts to matter more than the capacity. The chart is drawn from the published cells; the range bars are the chart’s own bands and nothing on this page was estimated.

What the number is measured at, and why a basement is the hard case

There is a second thing the figure does not say out loud, and it decides whether the number on the box is the number you get.

Capacity is normalised to a standard ambient temperature and relative humidity. For a portable dehumidifier the test procedure sets that condition at 65 °F dry-bulb and 60% relative humidity. For a whole-home unit it is 73 °F. The industry standard behind the test lowered the portable figure from 80 °F to 65 °F, which is why a machine that was sold as a 60-pint unit years ago carries a much smaller honest number today: the hardware is unchanged and the test condition is not.

The same document also says something that is easy to read past. Dehumidifiers “may encounter temperatures between 55 °F and 80 °F depending on their installation and operating conditions”. So the machine’s working life spans a 25-degree range, and its rating is pinned at one point inside it. A basement that sits at 60 °F is inside the range the unit is expected to see and below the condition it was rated at.

That makes the label figure a ceiling rather than a promise. It is the water the unit moves at 65 °F, and a colder room is not that room. The practical reading is simple: the chart cell tells you which class of machine to buy, and the temperature tells you whether the class works in your space at all. A unit sized for 50 pints and run in a room cold enough to frost the coil does not deliver 45; it can cycle on and off without removing moisture, which the sizing guidance says outright.

If you already own a unit and it is running without producing water, that is a different question from this one — the checks for a unit that is not collecting water run through the temperature, the setting, the coil and the drain in the order they normally fail.

Size for the worst week, not the average

The dampness axis on the chart is a condition, and a condition in a basement has a peak. The chart asks what the space is like without a dehumidifier, and most people answer that from how it feels on an ordinary day. The peak is a different day, and it is the day the machine has to survive.

This is the pattern behind the question owners keep asking about long service: machines that handled the first couple of humid seasons and then stopped keeping up. Read as a sizing story rather than a reliability story, it is what choosing the average looks like. A unit picked for an ordinary afternoon is correctly sized for eleven months and undersized for the month that matters, and the month that matters is the one that decides whether the space stays dry.

It also settles the running-cost question, which is usually put the other way round. A unit sized to the peak reaches the target and cycles off; a unit sized to the average reaches the same target by running continuously, which is the mode that costs the most to operate. Oversizing a dehumidifier is not the mistake it is on an air conditioner, where a short cycle leaves the room clammy. Here the published advice is to round toward the larger size, and the reason is the peak.

What the pints figure does not cover

Where the water goes. The rate says nothing about the tank. At 50 pints a day that is 6.25 US gallons, and a tank measured in the same pints will not hold a day of it.
The temperature the room actually sits at. The rating is at one condition and the unit may meet a 25-degree span. Below roughly 65 °F a condensing coil can frost, and that is a different machine rather than a bigger number.
Air exchange with the rest of the house. A basement open to the stairs is handed new humid air every hour. Capacity is a rate against a load, and the load is not in the chart.
Water arriving through the structure. A dehumidifier removes water from air. Seepage through a wall or a floor is a drainage problem, and a correctly sized machine will run continuously and lose.

Questions this page answers

How many pints dehumidifier do I need?: Read it off the published sizing chart, in pints per day. Under 2,000 square feet the cells are 20 to 30 pints a day if the space is slightly to moderately damp, 25 to 40 if it is very damp, and 30 to 50 if it is wet. Over 2,000 square feet they read 30 or more, 40 or more and 50 or more. The figure is a rate — water removed per day — not the amount the tank holds.
Is 20 pints enough for a basement?: It is the bottom of the first cell, not a recommendation. The published band for a space under 2,000 square feet that is slightly to moderately damp is 20 to 30 pints a day, so 20 is the floor of that band. Read the top of the band you land in rather than the bottom, and pick the band by the worst month rather than an average afternoon.
What is the difference between a 50-pint dehumidifier and a 50-pint tank?: One is a rate and the other is an amount. The capacity figure is pints of water removed per 24 hours under specified ambient conditions; the tank figure is pints of water the tank holds before it needs emptying. Both are printed in pints on the same product page, and only the first one is the number the sizing chart speaks in.
How many pints are in a gallon?: Eight US pints to a US gallon. That is why the capacity figure scales quickly: a 50-pint day is 6.25 US gallons of water in 24 hours, and no tank measured in the same pints holds a day of it.
How many times a day does a dehumidifier tank need emptying?: Divide the daily rate by what the tank holds. A unit rated 50 pints a day against a tank that holds 20 pints is two and a half fills a day, which is a tank emptied every nine and a half hours. That division is ours; the 24-hour basis and the tank figure are the published ones.
What is the best dehumidifier for a basement right now?: There is no single best, because the answer is a cell rather than a model. The machine that fits a basement is the one whose capacity sits in the published cell for that basement's floor area band and dampness, at the temperature the space actually runs. A ranking that does not name your cell is answering a different question, and one that is quoted on the older 80 degree rating basis is quoting a different quantity.
Does a cold basement change how many pints I need?: It changes whether any figure applies. Capacity is normalised to 65 degrees Fahrenheit dry-bulb and 60 percent relative humidity for a portable unit, while the same test procedure notes units may encounter 55 to 80 degrees in service. A room below the rating condition gets less than the label, and below roughly 65 degrees the condensing coil can frost, which is a different machine rather than a bigger number.

Where these numbers come from

The definition of product capacity as pints collected per 24 hours of operation under specified ambient conditions, the 65 °F dry-bulb and 60% relative humidity test condition for portable units, the 73 °F condition for whole-home units, the change from the earlier 80 °F standard, and the statement that dehumidifiers may encounter 55 °F to 80 °F in service are all from the US Department of Energy’s test procedure for dehumidifiers, which is 10 CFR 430 Appendix X1. The capacity bands, the three dampness descriptions and their humidity ranges are from ENERGY STAR’s dehumidifier sizing guidance, which is the AHAM-derived chart. The eight-pints-to-a-gallon figure is the standard US conversion. The tank-emptying divisions, the 6.25-gallon figure and the nine-and-a-half-hour example are our own arithmetic from those published numbers and are labelled as ours. Nothing on this page is a test result, and no number here was estimated.