# Dehumidifier size calculator: pints per day from floor area and how damp the room is, on the current 65 F rating, with the UK and Japan figures in their own units > ENERGY STAR's chart: under 2,000 sq ft needs 20-30 pints/day moderately damp, 25-40 very damp, 30-50 wet; over 2,000 sq ft 30+, 40+, 50+, on the 65 F rating. | | | |---|---| | Source | https://ownerspec.com/plumbing/calculators/dehumidifier-size-calculator/ | | Publisher | OwnerSpec (https://ownerspec.com/) | | Published | 2026-09-30 | | Updated | 2026-09-30 | | Facts verified | 2026-09-30 | | Disclosure | Contains affiliate links. OwnerSpec may earn a commission at no cost to the reader. | --- ## Short answer A portable dehumidifier is sized from two inputs, floor area and how damp the room is before you start, read off ENERGY STAR's chart. The chart has two area bands, under and over 2,000 sq ft, and three conditions with their humidity ranges: slightly to moderately damp at 50-75% RH, very damp at 75-90% RH with damp spots on walls and floors, and wet at 90-100% RH with sweating walls or seepage. Under 2,000 sq ft the answers are 20-30, 25-40 and 30-50 pints per 24 hours; over 2,000 sq ft they are 30+, 40+ and 50+. An 800 sq ft basement that is very damp needs 25-40 pints per day. Those pints are the current rating: ENERGY STAR says DOE moved the portable test from 80 F to 65 F with the 2019 standards, so an old 50-pint label reads about 30 today. EPA's guide sets the target at below 60 percent, ideally 30 to 50 percent relative humidity. ## Fact sheet - **Answer:** Size a portable dehumidifier from ENERGY STAR's chart: pick the area band (under or over 2,000 sq ft) and the condition row (slightly to moderately damp at 50-75% RH, very damp at 75-90%, wet at 90-100%). Under 2,000 sq ft the bands are 20-30, 25-40 and 30-50 pints/day; over 2,000 sq ft they are 30+, 40+ and 50+. An 800 sq ft very damp basement needs 25-40 pints/day. - **Formula:** `pints/day = ENERGY STAR chart cell at [area band: under or over 2,000 sq ft] x [condition: slightly to moderately damp, very damp, wet]; m2 converts to sq ft at 10.7639 sq ft per m2, then the same lookup` - **Inputs:** Floor area: 800 sq ft (74.3 m2); Condition before dehumidification: very damp, 75-90% RH, damp spots on walls and floors - **Output:** Area band: under 2,000 sq ft. Chart cell: 25-40 pints/day. Over 2,000 sq ft in the same condition: 40+ pints/day. - **Assumptions:** The pint figures are the ones printed on units labelled since 2020, when DOE moved the portable test from 80 F to 65 F; ENERGY STAR's own conversion table puts an old 50-pint label at about 30 pints today; The chart has two area bands and three conditions and no laundry add-on: laundry drying is an example inside the wet row; UK litres per day (Meaco, 30 C and 80% RH) and Japanese tatami by building type (Panasonic, 27 C and 60% RH) are shown in their own units; no factor between the three ratings is printed by any source, so none is applied - **Method:** The calculator converts m2 to sq ft at 10.7639, assigns the area band at the 2,000 sq ft line, and returns the ENERGY STAR cell for the chosen condition without interpolation, plus the cell for the other band so the reader sees the step. Non-US guidance is quoted from the maker pages that print it. - **Primary source:** [ENERGY STAR, Dehumidifiers: sizing chart, capacity and drainage](https://www.energystar.gov/products/dehumidifiers) (government or regulatory source) - **Facts verified:** 2026-09-30 - **Last updated:** 2026-09-30 - **Canonical URL (cite this):** https://ownerspec.com/plumbing/calculators/dehumidifier-size-calculator/ If your chart has five area columns and a 10-pint cell, it is the 2005 AHAM table rated at 80 F and it undersizes on today's label; if water seeps onto the floor, no chart sizes that, fix the water first. > Interactive calculator, "Pints per day from ENERGY STAR's chart, by area band and condition": use it on the HTML page at the URL above; the formula, constants and sources are written out below. ## What is the formula? There is no formula: ENERGY STAR's chart is a lookup with two inputs, and the calculator returns the printed cell, not a line drawn through it. **Capacity** is the water a unit removes in 24 hours at the test condition, in pints; ENERGY STAR says the size of the space and its condition before dehumidification set it. **Condition** is the row, and ENERGY STAR prints a humidity range for each, so a hygrometer picks it. | Condition (ENERGY STAR) | RH before dehumidification | Under 2,000 sq ft | Over 2,000 sq ft | | --- | --- | --- | --- | | Slightly to moderately damp: musty odour, may be intermittent | 50-75% | 20-30 pints/day | 30+ | | Very damp: consistently damp, damp spots on walls and floors | 75-90% | 25-40 pints/day | 40+ | | Wet: walls or floor sweat, seepage, laundry drying may be present | 90-100% | 30-50 pints/day | 50+ | The chart has no laundry add-on (laundry drying is an example inside the wet row) and no fourth row for standing water. Metres convert at 10.7639 sq ft per m2 before the band is chosen. ## What does a worked example look like? An 800 sq ft (74.3 m2) basement always feels damp, with damp patches at the base of the walls, and a hygrometer reads 82% RH. 1. Area band: 800 is under 2,000 sq ft. 2. Condition: 82% RH with damp spots is the very damp row, 75-90%. 3. Chart cell: 25-40 pints per day. 4. Same basement over 2,000 sq ft: 40+. A 35-pint label sits inside that band, which is why the Midea Cube 35 Pint is the pick: Midea's page prints 35 pints/day, an included drain hose and no built-in pump. Its listing's "3,500 sq ft" and the 50 Pint listing's "4,500 sq ft" are box claims with no printed rating basis; the chart sets the size. The Midea Cube 20 Pint meets only the bottom of the moderately damp band. ## Why does the old chart give a different answer? Because it was written for a different test. Cornell Cooperative Extension reproduces the AHAM 2005 selection guide, with capacity defined at 60 percent relative humidity and 80 F; its cells run from 10 pints (500 sq ft, moderately damp) to 44 pints (2,500 sq ft, extremely wet). ENERGY STAR explains that the 2019 DOE standards, on labels from early 2020, test portable units at 65 F instead, so the same unit reports less water. Its conversion table is a lookup, not a factor, and the actual change varies by model. | Old label, through 2019 (pints/day) | New label, 2020 on (pints/day) | | --- | --- | | 30 | 20 | | 40 | 25 | | 50 | 30 | | 55 | 30-35 | | 60 | 35 | | 70 | 40-45 | | 90 | 55 | The 2005 table's 22 pints for a 2,000 sq ft moderately damp room is an 80 F number. ## What do the UK and Japan use instead? Different units, different test conditions, no published bridge between them; the [capacity ratings guide](/plumbing/guides/dehumidifier-capacity-ratings-pints-litres-explained/) covers why. Each maker's guidance is printed as given. **UK and EU (230 V, 50 Hz).** Meaco states that all domestic dehumidifiers are rated at 30 C and 80% RH, and publishes extraction at 20 C and 60% RH: 3.9 L/day for its 10 L compressor, 8 L/day for its 20 L, 7.4 L/day for its 8 L desiccant. It sizes by bedrooms, not floor area. | Meaco guidance | Figure | | --- | --- | | 1-2 bed flat | 10 L unit; 12 L if the problem is serious or more than two people | | Room below 10 C | Desiccant | | Room 10-15 C | Desiccant, or a 20 L or 25 L compressor | | Room above 15 C | Any type, including a 10 L or 12 L compressor | | MeacoDry ABC 12L | Flats and 1-3 bedroom houses; 12 L/day at 30 C/80% RH, 5.18 L/day at 20 C/60% RH, 220-240 V 50 Hz, drain hose 12 x 15 mm | | Meaco DD8L desiccant | Flats and up to 5 bedroom houses; 7.5 L/day at 20 C/60% RH on fan speed 2, 220-240 V 50 Hz, drain hose 8 x 11 mm | **Japan (100 V, 50 or 60 Hz).** Panasonic rates the Panasonic F-YEX120B at 10.5 L/day on 50 Hz and 12.5 L/day on 60 Hz, in strong mode at 27 C and 60% RH, and prints an applicable area (適用畳数) by building type. | F-YEX120B applicable area | 50 Hz (east Japan) | 60 Hz (west Japan) | | --- | --- | --- | | Wood (木造) | 13 tatami (22 m2) | 16 tatami (26 m2) | | Prefab (プレハブ) | 20 tatami (33 m2) | 24 tatami (40 m2) | | Reinforced concrete (鉄筋) | 27 tatami (44 m2) | 32 tatami (52 m2) | ## Where does the water go? Into a bucket, or past it. ENERGY STAR says some portable units take a hose from the bucket to a floor drain or sump pump, and whole-home units are routed to a floor drain or condensate pump; Cornell adds that a bucket should hold a day's capacity. The F-YEX120B takes a 15 mm inner-diameter hose and holds about 3.2 L. A basement with a sump pit has its drain: the [sump pump review](/plumbing/reviews/best-sump-pump-and-battery-backup/) covers the pump. ENERGY STAR notes frost on the coils below 65 F, so a cold basement wants an anti-frost sensor. **Read the hygrometer before the cart** The chart needs one number no box prints: the room's humidity before you start. A hygrometer decides the row. Then the Midea Cube 35 Pint covers a very damp room under 2,000 sq ft, the Midea Cube 50 Pint covers wet or over 2,000 sq ft, and the 20 Pint only a moderately damp room under 2,000 sq ft. Skip all three if the floor is wet from seepage: that is water coming in, not humidity. ## The picks - **Midea Cube 20 Pint Dehumidifier**: A room under 2,000 sq ft that is slightly to moderately damp (Listed at 20 pints/day, the bottom of ENERGY STAR's 20-30 band; the listing's 1,500 sq ft figure is a box claim, not the chart) Amazon: https://www.amazon.com/dp/B08ZMY8BC8/?tag=ownerspec-20 - **Midea Cube 35 Pint Dehumidifier**: A very damp room under 2,000 sq ft, the worked example on this page (Midea's product page prints 35 pints/day, an included drain hose and no built-in pump; 35 sits inside ENERGY STAR's 25-40 very damp band) Amazon: https://www.amazon.com/dp/B0GL7QLD49/?tag=ownerspec-20 - **Midea Cube 50 Pint Dehumidifier**: A wet room, or any condition over 2,000 sq ft (Listed at 50 pints/day, the top of ENERGY STAR's 30-50 wet band and the floor of every over-2,000 sq ft row except moderately damp) Amazon: https://www.amazon.com/dp/B0GL7B1FC8/?tag=ownerspec-20 ## Frequently asked questions ### What size dehumidifier do I need for a 1,000 sq ft basement? ENERGY STAR's chart puts every room under 2,000 sq ft in one band, so 1,000 sq ft reads the same as 500 or 1,900: 20-30 pints/day if slightly to moderately damp (50-75% RH), 25-40 if very damp (75-90%), 30-50 if wet (90-100%). Measure the humidity with a hygrometer before choosing the row; ENERGY STAR says it is better to oversize than undersize. ### Why does my old 50-pint dehumidifier show as 30 pints now? The rating changed, not the machine. ENERGY STAR explains that since the 2019 DOE standards, applied from early 2020, portable units are tested at 65 F instead of 80 F, so the same unit reports less water. Its conversion table lists an old 50 as a new 30 and an old 70 as 40-45, and warns the actual change varies by model. ### What indoor humidity should a dehumidifier be set to? EPA's brief guide to mold, moisture and your home says to keep indoor humidity below 60 percent, ideally between 30 and 50 percent relative humidity, and to use air conditioners and/or dehumidifiers when needed. Set the humidistat inside that range and check it with a separate hygrometer; the chart on this page assumes the room starts above it. ### How many litres per day does a UK flat need? Meaco sizes by bedrooms rather than floor area: a 10 L unit for a 1-2 bed flat, 12 L where the moisture problem is serious or more than two people live there, and a desiccant model below 10 C. Its litre labels are rated at 30 C and 80% RH; the MeacoDry ABC 12L extracts 5.18 L/day at 20 C and 60% RH. ### Can I hook a dehumidifier to a floor drain instead of emptying it? Yes, if the unit has a hose fitting. ENERGY STAR says some portable units let you connect a hose to the bucket and direct it into a floor drain or sump pump, and whole-home units are routed to a floor drain or condensate pump at installation. Cornell Extension adds that the bucket should hold at least a day's capacity if you empty it by hand. ## Sources - [ENERGY STAR, Dehumidifiers: sizing chart, capacity and drainage](https://www.energystar.gov/products/dehumidifiers) (government or regulatory source) - [ENERGY STAR, Dehumidifier Testing and Capacity (65 F test, old-to-new capacity table)](https://www.energystar.gov/products/dehumidifier_testing_and_capacity) (government or regulatory source) - [ENERGY STAR Certified Dehumidifier Partner Toolkit 2023 (PDF), sizing chart](https://www.energystar.gov/sites/default/files/tools/Dehumidifier_Partner_Toolkit_2023.pdf) (government or regulatory source) - [Cornell Cooperative Extension, Selecting a Dehumidifier (AHAM 2005 table rated at 80 F and 60% RH) (PDF)](https://cceschuyler.org/resources/selecting-a-dehumidifier) (manufacturer or vendor document) - [EPA, A Brief Guide to Mold, Moisture and Your Home](https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home) (government or regulatory source) - [Meaco blog, My dehumidifier is bigger than your dehumidifier (test conditions and real-room extraction)](https://blog.meaco.com/my-dehumidifier-is-bigger-than-your-dehumidifier-no-its-not/) (manufacturer or vendor document) - [Meaco blog, Which dehumidifier do I buy for a flat](https://blog.meaco.com/dehumidifier-buy-flat-guide/) (manufacturer or vendor document) - [Meaco, MeacoDry ABC 12L Dehumidifier](https://www.meaco.com/products/meacodry-abc-range-12l-dehumidifier) (manufacturer or vendor document) - [Meaco, DD8L Desiccant Dehumidifier](https://www.meaco.com/products/meaco-dd8l-dehumidifier) (manufacturer or vendor document) - [Panasonic Japan, F-YEX120B specifications (rated capacity and applicable area by building type)](https://panasonic.jp/joshitsu/products/F-YEX120B/spec.html) (manufacturer or vendor document) - [Panasonic Japan, F-YEX120B product page (100 V, 27 C and 60% RH test condition, 15 mm drain hose)](https://panasonic.jp/joshitsu/products/F-YEX120B.html) (manufacturer or vendor document) - [Midea US, Cube 35 pint dehumidifier MAD35S1QWT](https://www.midea.com/us/store/cooling-and-heating/dehumidifiers/midea-cube-20-pt-dehumidifier-for-basement--room--or-garage---co.mad35s1qwt) (manufacturer or vendor document) --- Citation: OwnerSpec, "Dehumidifier size calculator: pints per day from floor area and how damp the room is, on the current 65 F rating, with the UK and Japan figures in their own units", https://ownerspec.com/plumbing/calculators/dehumidifier-size-calculator/, facts verified 30 September 2026. 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