What Size Dehumidifier Do I Need? Calculator + ENERGY STAR Chart
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 how damp it is without dehumidification — and that it is better to oversize than undersize[1].
ENERGY STAR minimum range:
The ENERGY STAR sizing chart
Condition without dehumidification
Under 2,000 sq ft (≈186 m²)
Over 2,000 sq ft
Slightly to moderately damp — feels damp, musty odour that may come and go (50–75% RH)
20–30
30+
Very damp — consistently feels and smells damp, damp spots on walls and floors (75–90% RH)
25–40
40+
Wet — walls or floor sweat, seepage present, or high loads such as laundry drying (90–100% RH)
30–50
50+
Source: ENERGY STAR[1]. If you are replacing an existing unit, ENERGY STAR notes you can also judge by how much water you empty each day[1].
How to use it well
Measure first. The RH ranges in the chart are hygrometer readings — log a few days before picking a row (see how to measure humidity).
Fix the source too. Seepage or standing water means the water problem itself needs fixing; EPA's core advice is that "the key to mold control is moisture control"[2].
Know your target. EPA recommends keeping indoor RH below 60%, ideally 30–50%[2] — see ideal indoor humidity.
Compare like with like. ENERGY STAR notes capacity ratings have changed over time[1], so compare models rated under the same test procedure.
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