Dehumidifier Size Calculator
Dehumidifiers are rated by how many pints of water they pull from the air each day. Sizing one for a space multiplies the room area in square feet by a dampness factor in pints per day per square foot, with the factor rising from slightly damp to wet to very wet conditions. Because that factor depends on your specific room, it is an input you choose from a sizing guide. This calculator returns the required capacity in pints per day and converts it to liters per day for metric-labeled units.
Dehumidifier sizing formula
Room area = length * width
Capacity (pints/day) = area * dampness factor
Capacity (liters/day) = pints per day * 0.473176
Capacity (gallons/day) = pints per day / 8
One US liquid pint equals 0.473176 liters and there are 8 pints in a US gallon, both exact conversions. The dampness factor is your input for the room condition, so the capacity reflects your actual space rather than an assumed default.
Dehumidifier sizing notes
- Capacity is the pints of water removed per 24 hours, the standard appliance rating.
- The dampness factor rises from slightly damp through wet to very wet conditions.
- One US pint equals 0.473176 liters; there are 8 pints in one US gallon.
- An undersized unit runs continuously without reaching the target humidity.
- High ceilings hold more moisture, so step up the factor or the next capacity tier.
Dehumidifier size: frequently asked questions
What size dehumidifier do I need?
Capacity is rated in pints of water removed per day. A common sizing method multiplies the room area in square feet by a dampness factor in pints per day per square foot, where the factor rises with how damp the space is. This calculator multiplies your area by the factor you select for your conditions and reports pints and liters per day.
What dampness factor should I use?
The factor depends on whether the space is merely damp, wet, very wet, or has standing moisture, and it is not a single fixed number. Use a value from a manufacturer or appliance-efficiency sizing guide that matches your room's condition. Because it varies, this calculator takes the factor as your input rather than assuming one.
Why is capacity given in pints per day?
Dehumidifier capacity is the volume of water the unit can extract from the air in 24 hours, conventionally stated in US pints per day. Manufacturers label units by this figure. The calculator also converts pints to liters, since one US liquid pint is 0.473176 liters, for products labeled in metric units.
Does a bigger dehumidifier cost more to run?
A right-sized unit reaches the target humidity and cycles off, while an undersized unit runs continuously and may never catch up. A modestly larger capacity often runs less and more efficiently in a very damp space. Match the capacity to the calculated pints per day rather than guessing high or low.
Should I account for room height?
This area-based method assumes a standard ceiling height, which is how most appliance sizing charts are built. A room with an unusually high ceiling holds more air and moisture, so step up the dampness factor or the next capacity tier. For precise control, consult the manufacturer sizing guidance.
Official sources
- U.S. Environmental Protection Agency: ENERGY STAR Dehumidifiers.
- U.S. National Institute of Standards and Technology: Unit conversion (pint, liter, gallon).
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.