About the Dehumidifier Size Calculator
This dehumidifier size calculator recommends how many pints of water per day your dehumidifier should be able to remove. Enter the floor area of the room, basement or crawlspace and pick how damp it is — from a slightly musty space to one with visible water — and it returns a minimum capacity in pints and litres per day and the nearest standard size to shop for.
It is designed for homeowners dealing with a damp basement, musty bedroom, laundry room or garage, and for renters wondering whether a small unit is enough. Getting the size right matters: an undersized dehumidifier runs constantly without reaching your target humidity, while a correctly sized one cycles off and uses less electricity.
Recommendations follow the ENERGY STAR capacity table, which uses the current US Department of Energy test method introduced in 2019. Capacities under that method are lower than older ratings for the same machine — a unit once sold as 70 pints is often labelled about 50 pints today — so compare models using the new figure. ENERGY STAR gives ranges for spaces under 2,000 sq ft; this tool interpolates within that range by area and scales proportionally for larger spaces.
With the default inputs, the minimum capacity is 32.5 pints/day. Change any value above to recalculate instantly.
How to use the dehumidifier size calculator
- 1Measure the floor area of the room or basement (length × width).
- 2Choose square feet or square metres and enter the area.
- 3Pick the dampness level that best describes the space.
- 4Read the minimum pints per day and the standard size to buy.
Formula and method
ENERGY STAR publishes a recommended capacity range for each dampness level: 20–30 pints per day for slightly to moderately damp spaces, 25–40 for very damp spaces and 30–50 for wet spaces, for rooms under 2,000 sq ft, with larger spaces needing more. This calculator places your space within that range in proportion to its area — a tiny room gets the low end, a 2,000 sq ft space the high end — and above 2,000 sq ft scales the top of the range in proportion to area.
The result is rounded up to the next common retail size (20, 22, 30, 35, 50 pints and so on). One US pint is 0.473 litres. Capacities refer to the 2019 DOE test at 65°F and 60% relative humidity; older ratings measured at 80°F are higher for the same machine.
- Low, High
- ENERGY STAR capacity range for the chosen condition
- Area
- Floor area of the space in square feet
Worked examples
Very damp 1,000 sq ft basement
A very damp space has an ENERGY STAR range of 25–40 pints. At 1,000 sq ft — halfway to 2,000 — the calculator recommends 25 + 15 × 0.5 = 32.5 pints a day, so a 35-pint dehumidifier is the right size.
Musty 500 sq ft bedroom
A slightly damp room uses the 20–30 pint range. At 500 sq ft that gives 20 + 10 × 0.25 = 22.5 pints a day, just above a 22-pint unit, so a 30-pint model is the safer choice.
Wet 2,500 sq ft basement with seepage
Wet spaces need 50 pints at 2,000 sq ft. Scaling to 2,500 sq ft gives 50 × 2,500 ÷ 2,000 = 62.5 pints a day, so look for a 70-pint unit or a whole-home system — and fix the water source too.
Frequently asked questions
What size dehumidifier do I need for a basement?+
A typical 1,000 sq ft basement that feels damp and smells musty needs about 25–35 pints per day under the current DOE ratings. If there are damp spots or seepage, size up to 35–50 pints or more.
Why are dehumidifier pint ratings lower than they used to be?+
In 2019 the Department of Energy changed the test from 80°F to 65°F, which better reflects basements. Machines remove less water in cooler air, so a unit formerly rated 70 pints is now usually labelled around 50 pints.
Is it better to oversize a dehumidifier?+
Slightly oversizing is fine and is what ENERGY STAR recommends — a larger unit reaches the target humidity faster and cycles off. A badly undersized unit runs continuously and may never get the space below 50% humidity.
What humidity should I set my dehumidifier to?+
Aim for 30–50% relative humidity indoors. Keeping it below about 50–60% discourages mould, dust mites and musty odours, while going much lower wastes energy and can make the air feel dry.
How do I convert pints per day to litres?+
Multiply pints by 0.473. A 35-pint dehumidifier removes about 16.6 litres a day and a 50-pint model about 23.7 litres a day under the standard test conditions.