Dehumidifier Size Calculator
Enter your room and how damp it feels to see the capacity ENERGY STAR recommends, then estimate what it costs to run.
Sample numbers only, to show how it works. Replace them with yours.
Enter the floor area of the space in square feet (length times width).
This is an estimate, not a professional calculation. See the disclaimer and the methodology.
How it is calculated
The calculator uses the ENERGY STAR charts for a portable dehumidifier. They give a recommended range of capacity in pints per day by the size of the room (under 2,000 square feet, or larger) and by how damp the space is.
The chart has three levels of dampness: slightly to moderately damp (50% to 75% relative humidity), very damp (75% to 90%) and wet (90% to 100%, with high-load conditions such as laundry drying). The calculator asks you to pick the closest. If you have a hygrometer, it shows the relative humidity.
Pints per day is how much water the unit can remove in 24 hours under test conditions. ENERGY STAR says it is better to oversize than undersize.
For the running cost, the energy is the water removed divided by the Integrated Energy Factor (IEF), the liters of water removed for each kWh. A US pint is 0.473176 liters. Cost = kWh × price per kWh. The price starts at the 2024 annual state average from EIA. Use the water the unit really removes in a day, which can be less than its rating, and the IEF on its listing.
The ENERGY STAR minimum IEF depends on the capacity: 1.70 up to 25 pints, 2.01 from 25.01 to 50 pints and 3.30 above. Whole-home dehumidifiers have their own rules, and ENERGY STAR gives no sizing numbers for them.
Worked examples
A very damp 1,200 square foot basement
The chart gives 25 to 40 pints per day for a very damp space under 2,000 square feet.
A large wet space
A wet space of 2,500 square feet falls in the large-room column, which asks for 50 or more pints per day.
What a unit costs to run
A dehumidifier that removes 20 pints a day with an IEF of 2 liters per kWh uses 4.7 kWh a day. At the U.S. average of 16.5 cents (2024) that is $0.78 a day and $23 per 30 days. The pints and the IEF are assumed for this example.
Frequently asked questions
What size dehumidifier do I need?
It depends on the size of the space and how damp it is. Enter both and the calculator returns the ENERGY STAR range in pints per day.
How do I know how damp my space is?
A musty smell and clammy air suggest a damp space, and visible moisture or water on the floor suggests a wet one. A hygrometer reads relative humidity: 50% to 75% is slightly to moderately damp, 75% to 90% very damp and 90% or more wet, according to the ENERGY STAR chart.
Is a bigger dehumidifier better?
ENERGY STAR says it is better to oversize than undersize. A larger unit removes the water faster and runs less to hold the level, but costs more to buy.
What does IEF mean?
Integrated Energy Factor is the liters of water a dehumidifier removes for each kWh. A higher number means less electricity for the same water. For portable units, the ENERGY STAR minimum is 1.7 up to 25 pints per day.
Does this work for a whole house?
No. ENERGY STAR gives no sizing numbers for whole-home dehumidifiers and points to a contractor. This calculator is for portable units.
Related calculators
Sources and last update
- ENERGY STAR, Dehumidifiers (recommended capacity by room size and dampness)
- ENERGY STAR, Dehumidifiers key efficiency criteria (minimum IEF)
- U.S. Energy Information Administration, 2024 Average Monthly Bill, Residential (average price by state)
Last updated: November 3, 2026. See methodology and sources.