Dehumidifier Size Calculator
Estimate adjustable daily moisture-removal capacity, dehumidifier quantity, room volume, electricity use and monthly operating cost.
Default project preview
60 pints/day
Room volume
4,000 ft³
Base moisture load
48 pints/day
Installed capacity
70 pints/day
Daily electricity
12 kWh
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Room length
Enter this project assumption in ft. The current imperial default is 25 ft.
Room width
Enter this project assumption in ft. The current imperial default is 20 ft.
Ceiling height
Enter this project assumption in ft. The current imperial default is 8 ft.
Moisture-load rate
Enter this project assumption in pints/day per 1,000 ft³. The current imperial default is 12 pints/day per 1,000 ft³.
Capacity reserve
Enter this project assumption in %. The current imperial default is 25 %. Minimum: 0. Maximum: 100.
Rated capacity per unit
Enter this project assumption in pints/day. The current imperial default is 35 pints/day.
Power per unit
Enter this project assumption in W. The current imperial default is 500 W.
Expected runtime
Enter this project assumption in hours/day. The current imperial default is 12 hours/day. Minimum: 0. Maximum: 24.
Electricity price
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
How to read the outputs
Room volume
rectangular room. Default preview: 4,000 ft³.
Base moisture load
before reserve. Default preview: 48 pints/day.
Installed capacity
2 full units. Default preview: 70 pints/day.
Daily electricity
12 runtime hours. Default preview: 12 kWh.
Monthly electricity
30-day estimate. Default preview: 360 kWh.
Monthly energy cost
entered electricity rate. Default preview: $64.80.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Base moisture capacity = room volume ÷ rate-volume basis × entered moisture-load rate. Reserve is applied, then unit quantity is rounded up by rated capacity.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Estimate preliminary moisture-removal capacity from space area, conditions and moisture severity.
Calculation steps
- 1Enter the actual project dimensions or operating values.
- 2Apply the calculator formula using consistent units.
- 3Review the unrounded result and the editable allowance.
- 4Round only to the product, stock length or equipment increment actually purchased.
Worked numerical example
A 1,000 ft² damp basement may require a larger rated daily capacity than the same area under mildly humid conditions.
Purchasing and rounding
Select equipment by its rated moisture-removal capacity at conditions reasonably close to the space being treated. Do not buy solely from floor area: persistent water entry, low temperatures, open connections to other rooms and drying loads can require a different capacity or a separate moisture-control solution.
Interpret the result
The result is a preliminary capacity range for moisture removal, not a guarantee of indoor relative humidity. If the space has bulk-water intrusion or major air leakage, correcting those sources can matter more than increasing dehumidifier size.
Page-specific assumptions
- Inputs describe one consistent project condition.
- Entered yields and efficiencies match the selected product or equipment.
- Site-specific code and engineering requirements are checked separately.
Common mistakes
- Mixing imperial and metric inputs.
- Using nominal dimensions where actual coverage controls.
- Rounding intermediate values too early.
- Treating a quantity estimate as design approval.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Dehumidifier Size Calculator questions
Why is the moisture-load rate editable?+
Moisture generation and infiltration vary too much for room volume alone to determine capacity accurately.
Why might rated capacity not be achieved?+
Dehumidifier ratings use specified temperature and humidity conditions. Cooler or drier rooms can reduce extraction.
Should water intrusion be fixed first?+
Yes. Leaks, groundwater and uncontrolled humid-air entry should be addressed rather than relying only on dehumidification.