Dehumidifier Sizing Calculator

Work out dehumidifier sizing instantly with clear inputs, formula shown and shareable results.

About Dehumidifier Sizing Calculator

Dehumidifier capacity is quoted in pints of water removed per day and is sized from floor area banded by how damp the space is: roughly 10 pints per 500 ft² for a musty space, 14 for visible damp and 18 where there is seepage. Ceiling height scales the result because the moisture load follows the air volume.

Formulas

Moisture load

pints/day = (area / 500) x dampness rate x (ceiling height / 8)

Metric

L/day = pints/day x 0.4732

Worked example

With the default values below, Dehumidifier Sizing Calculator returns Moisture removal required of 16.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Floor areaminimum 1 ft²: 800 ft²
Ceiling heightminimum 1 ft: 8 ft
Dampness levelone of Moderately damp — musty in humid weather, Very damp — damp spots on walls, Wet — standing water or seepage: Moderately damp — musty in humid weather

Results

Moisture removal required: 16.0 pints/day
Equivalent metric capacity: 7.6 L/day
Unit size to specify: 20 pints/day
Space volume: 6,400 ft³

Step by step

1Values used
2Moisture load
3Metric
4Moisture removal required= 16.0 pints/day
5Equivalent metric capacity= 7.6 L/day
6Unit size to specify= 20 pints/day
7Space volume= 6,400 ft³

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Dehumidifier Sizing figure worked out?

pints/day = (area / 500) x dampness rate x (ceiling height / 8). Dehumidifier capacity is quoted in pints of water removed per day and is sized from floor area banded by how damp the space is: roughly 10 pints per 500 ft² for a musty space, 14 for visible damp and 18 where there is seepage.

Does it matter where the unit sits?

Yes. Capacity ratings assume free air movement and about 65 percent relative humidity at 80 °F. A cold basement or a unit boxed into a corner delivers considerably less than nameplate.

What values do I need to enter?

This calculator takes 3 inputs: Floor area, Ceiling height, Dampness level. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.