What Size Dehumidifier Do I Need?

Tell us the room size and how damp it feels and this free calculator gives you the pints-per-day range from the current Energy Star sizing chart. It also gives you the answer the retailer charts skip: in Phoenix's dry climate, your air conditioner may already be doing the job, so you might not need one at all.

Built by Mold Pros Phoenix · Updated June 28, 2026 · Current Energy Star (post-2019 standard) sizing + the EPA 30-50% humidity target

Size your dehumidifier

How dehumidifier sizing works

Dehumidifier capacity is measured in pints per day, which is how much water it pulls from the air in 24 hours. You size it two ways at once: how big the space is, and how damp it feels. Bigger and damper means more pints. There is no official "pints per square foot" formula (the "1 pint per 50 sq ft" line you will see is a rule of thumb, not a standard), so the honest output is a range, not a single number. When you land between two sizes, go up.

The point of sizing it right is not the number itself; it is the goal. The EPA says to keep indoor humidity below 60%, and "Indoor relative humidity (RH) should be kept below 60 percent -- ideally between 30 percent and 50 percent, if possible." A dehumidifier is just the tool for holding a space in that range when air conditioning alone can't.

Dehumidifier sizing chart (current Energy Star standard)

Pints per day by room size and dampness, current Energy Star standard. A starting range, not an exact spec.

Dehumidifier capacity (pints per day) by dampness and room size, current Energy Star standard.
How damp it feels	Up to 2,000 sq ft	Over 2,000 sq ft
Damp (about 50-75% RH)	20-30 pints/day	30+ pints/day
Very damp (about 75-90% RH)	25-40 pints/day	40+ pints/day
Wet (about 90-100% RH)	30-50 pints/day	50+ pints/day

Dehumidifier pint ratings changed in 2019: the DOE test moved from 80°F to a cooler 65°F, so the same machine is now rated for fewer pints (an old 70-pint unit is rated about 40-45 pints today). Every number here uses the CURRENT (post-2019) standard. Don't compare it to an older unit's nameplate.

Do you even need a dehumidifier in Phoenix?

Here is the part the retailer sizing guides leave out, because they are there to sell you a unit: in a dry desert climate, you often do not need a standalone dehumidifier at all. A normal refrigerated air conditioner removes moisture as it cools and drips it out the condensate line, which usually keeps a typical Phoenix home well under the EPA's 60% ceiling on its own. A dehumidifier earns its keep in four specific situations:

A normal refrigerated air conditioner dehumidifies as it cools — it drips the moisture out at the coil and down the condensate line. In Phoenix's dry season that is usually enough to keep a typical home well under the EPA's 60% ceiling without any separate dehumidifier.
Evaporative 'swamp' coolers are the exception: they cool by ADDING moisture to the air, so they raise indoor humidity on purpose. When monsoon humidity climbs and the cooler stops keeping up, a dehumidifier (or switching to refrigerated AC) is what brings the room back down.
During monsoon season (roughly July-September), outdoor humidity spikes and any roof or flood intrusion can push a closed room over 60% RH. That is the time of year a dehumidifier earns its keep in the Valley.
A closed-up or snowbird home with the AC set high or off gets no dehumidification for months. A humidistat-controlled dehumidifier protects against musty buildup while you're away.

So before you buy: if you run refrigerated AC and the space only "feels a little humid," your money is better kept in your pocket. If you run a swamp cooler, it is monsoon season, the home sits closed up, or a specific room stays damp, a right-sized unit is worth it. And if walls or floors are actually sweating, that is a water problem a dehumidifier won't fix. To see whether your surfaces are at condensation risk, run the dew point calculator; for swamp-cooler homes specifically, see swamp cooler mold.

When a dehumidifier isn't the answer

A dehumidifier manages humidity in the air. It does not fix a roof leak, a slab leak, an AC condensate overflow, or mold that has already started. The EPA is blunt about the order of operations: "The key to mold control is moisture control." So if the dampness keeps coming back no matter how the dehumidifier runs, there is a water source to find and fix. If a space has been wet for more than a day or two, it is worth getting it checked before mold spreads. A Phoenix mold inspection finds the source and any growth before it gets expensive.

Sources (4): ENERGY STAR — Dehumidifiers (sizing chart) (2025); ENERGY STAR — Dehumidifier Testing and Capacity (2019 standard change) (2024); EPA — Mold Course, Chapter 2 (indoor humidity 30-50%) (2024); EPA — A Brief Guide to Mold, Moisture and Your Home (2024).

Common questions about dehumidifier sizing

What size dehumidifier do I need?

Match the room size to how damp it feels, then read the pint-per-day range off the current Energy Star chart. For a space up to 2,000 sq ft, that is roughly 20-30 pints/day if it is just damp, 25-40 if it is very damp, and 30-50 if it is wet; larger spaces start at 30, 40, and 50+ pints. Sizing is a guide, not an exact number, so when you are between two sizes, go up. The goal is to hold indoor humidity in the EPA range of 30-50%.

What size dehumidifier do I need for a basement or a 1,000 sq ft space?

A space around 1,000 sq ft falls in the "up to 2,000 sq ft" Energy Star tier: about 20-30 pints/day if it is damp, 25-40 if it is very damp, and 30-50 if walls or floors actually sweat. Basements tend to run damper than the rooms above them, so size for the dampness you measure, not the square footage alone, and go up a size if it is borderline.

Do I even need a dehumidifier in Phoenix?

Often, no. A normal refrigerated air conditioner pulls moisture out of the air as it cools, and in Phoenix's dry climate that usually keeps a typical home well under the EPA's 60% humidity ceiling on its own. A standalone dehumidifier earns its keep mainly with an evaporative (swamp) cooler running, during monsoon humidity spikes, in a closed-up or vacant home, or for one specific damp room. If none of those fit, you probably do not need one.

Does my air conditioner already dehumidify?

A refrigerated (compressor) AC does: it condenses moisture on the cold coil and drains it out the condensate line, lowering indoor humidity as it cools. An evaporative "swamp" cooler is the opposite: it cools by adding moisture, so it raises indoor humidity. That is the Phoenix split that decides whether a dehumidifier helps you or fights your own cooler.

Why are dehumidifier pint sizes different than they used to be?

In 2019 the Department of Energy changed the test conditions from 80°F to a cooler 65°F, which is more like a real basement. The same machine removes less water at the cooler temperature, so nameplate pint ratings dropped about 30%, and an old 70-pint unit is rated roughly 40-45 pints today. Use current-standard numbers and do not compare them to an older unit's label.

What humidity should I keep my home at to prevent mold?

The EPA recommends keeping indoor relative humidity below 60%, and ideally between 30% and 50%. That is the target a dehumidifier is sized to hold. There is no exact humidity at which mold switches on, but staying in that range keeps surfaces from holding the moisture mold needs.

Get a free, no-obligation Phoenix mold assessment

If a room stays damp no matter what, or walls and floors are sweating, the problem is a water source, not air. A fast, free assessment finds where the moisture is coming from and whether mold has started. No pressure and no scare tactics, just a straight answer.