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Dehumidifier size calculator

This dehumidifier size calculator uses the ENERGY STAR chart: the capacity you need depends on the size of the space and how damp it is without dehumidification. Enter the area and pick the condition to see the recommended pints per day, also converted to liters.

Example: Area of the space 500 · Unit: sq ft · Condition without dehumidification: Slightly to moderately damp (50–75 % RH) → Minimum capacity: Minimum capacity 20–30 pints/day (9.5–14.2 L/day). Source: ENERGY STAR (U.S. EPA), Dehumidifiers – Capacity: recommended capacity in pints per day; slightly to moderately damp (50–75 % RH) 20–30 / 30+, very damp (75–90 % RH) 25–40 / 40+, wet (90–100 % RH) 30–50 / 50+ for small-medium (<2,000 sq ft) / large rooms; better to oversize; frost below 65 °F (read 10.10.2026). Updated: .

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Result

Minimum capacity
Minimum capacity 20–30 pints/day (9.5–14.2 L/day)
All conditions
Condition – 500 ft², small to medium roomRecommended capacity
Slightly to moderately damp20–30 pints/day (9.5–14.2 L/day)
Very damp25–40 pints/day (11.8–18.9 L/day)
Wet30–50 pints/day (14.2–23.7 L/day)
Guide values from the ENERGY STAR chart, converted with 1 pint = 0.4732 L. It is better to oversize than undersize. Below 65 °F (18 °C) frost can form on the coils.

How it is calculated

A dehumidifier’s size is its capacity in pints of water removed per 24 hours. ENERGY STAR says the capacity you need depends on two things: the size of the space and its condition without dehumidification. If you are replacing a unit, you can judge by how much water you empty each day.

ENERGY STAR capacity chart

ConditionUp to 2,000 sq ftOver 2,000 sq ft
Slightly to moderately damp: musty odor, 50–75 % RH20–30 pints (9.5–14.2 L)30+ pints (14.2 L)
Very damp: smells damp, damp spots, 75–90 % RH25–40 pints (11.8–18.9 L)40+ pints (18.9 L)
Wet: walls or floor sweat, laundry drying, 90–100 % RH30–50 pints (14.2–23.7 L)50+ pints (23.7 L)

A 500 sq ft basement that feels very damp therefore needs a unit with at least 25 to 40 pints per day. ENERGY STAR adds that it is better to oversize than undersize, and that capacity ratings have changed – compare models by their current rating. The chart is meant for portable units; whole-home dehumidifiers are sized separately.

Practical tips

When surfaces will fog up is shown by the dew point calculator; how much air ventilation exchanges by the air changes per hour calculator.

Frequently asked questions

What size dehumidifier do I need for a 500 sq ft basement?

For a slightly to moderately damp space 20–30 pints per day, very damp 25–40 pints, wet 30–50 pints – according to the ENERGY STAR chart for rooms up to 2,000 sq ft.

How many liters is a 30-pint dehumidifier?

About 14.2 liters per day (30 × 0.4732 L).

Is it better to buy a bigger dehumidifier?

Yes, ENERGY STAR says it is better to oversize than undersize.

What counts as “wet”?

Walls or floor sweat, there is seepage, or laundry is dried in the room – about 90–100 % relative humidity.

Does a dehumidifier work in a cold basement?

Below 65 °F frost can form on the coils and the compressor may cycle on and off. Models for lower temperatures or with an anti-frost sensor help.

What if my space is larger than 2,000 sq ft?

ENERGY STAR then recommends at least 30, 40 or 50 pints per day depending on the condition.

Sources and legal basis

As of: · Editorial policy

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