What Size Dehumidifier Do I Need?
Get a sensible dehumidifier capacity range in pints per day for the size and dampness of your room.
Calculator
Free, runs entirely in your browser, and your numbers never leave your device. Results are estimates for planning only.
What this calculator does
This dehumidifier calculator suggests a capacity range in pints per day based on the room's floor area, its ceiling height, and how damp it feels, with adjustments for basements and for nearby moisture sources like a bathroom or laundry. It returns a range rather than a single number, because real moisture loads depend on conditions a calculator can't see.
How to use it
- Enter the room's floor area and ceiling height.
- Choose the dampness level that best matches what you notice — from a faint musty smell to standing moisture.
- Mark whether the room is a basement and whether a bathroom or laundry adds moisture nearby.
- Read the suggested pints-per-day range and aim near the top of it when in doubt.
The formula
Capacity ≈ a baseline pints-per-day range (per 500 sq ft) × (area ÷ 500) × (height ÷ 8 ft), increased about 10% for basements and about 15% for nearby bathroom or laundry moisture.
Example calculation
A 500 sq ft basement room with 8 ft ceilings, rated as 'damp', with no extra moisture source:
- Baseline for 'damp', per 500 sq ft: about 12–18 pints/day
- Area and height factor: 500 ÷ 500 × 8 ÷ 8 = 1.0
- Not flagged as basement in this example, no laundry: no adjustment
- Suggested range: roughly 12–18 pints/day
Result: Roughly 12–18 pints per day — choose a unit rated near the top of that range for margin.
Buying and planning tips
- When unsure, size up. A slightly larger unit cycles less, lasts longer, and copes better in humid spells.
- Fix the source of moisture too — grading, gutters, and sealing often matter more than the unit's size.
- Look at the unit's rating conditions; older and newer pints-per-day tests are measured differently.
Common mistakes to avoid
- Sizing only by floor area and ignoring how damp the room actually is.
- Picking the bottom of the range for a basement, then finding it runs constantly.
- Treating the pints-per-day rating as exact, when it is measured under standard lab conditions.
Assumptions and limits
- Baseline ranges are rough planning figures, not a published standard.
- Actual needs depend on outdoor humidity, air sealing, and ongoing moisture sources.
- Always cross-check sizing against AHAM and manufacturer guidance for your conditions.
Frequently asked questions
What size dehumidifier do I need for 1000 sq ft?
For a moderately damp 1000 sq ft space with 8 ft ceilings, plan on roughly 24 to 35 pints per day; a wetter room of the same size needs more. Enter your area, height, and dampness above to get a range tailored to your room.
What size dehumidifier do I need for a basement?
It depends on the area, ceiling height, and how damp the space is. A moderately damp 500 sq ft basement often lands in the 12 to 20 pints-per-day range, while a wet basement of the same size needs considerably more.
What size dehumidifier do I need for a 3 bedroom house?
Whole-home dehumidifying is best sized room by room, then totalled — or handled by a single larger whole-house unit. Run each damp room through the calculator and add the results, or step up to a 50–70 pint unit for an average three-bedroom home.
Why does the calculator give a range instead of one number?
Real moisture loads depend on outdoor humidity, how well the room is sealed, and ongoing sources like showers or laundry. A range is more honest than a single figure that pretends to know all of that.
Are dehumidifiers rated in pints per day?
Yes. The rating is how many pints of water a unit removes in 24 hours under standard test conditions, which are often more humid than a typical room, so real-world removal can be lower.
Does a basement need a bigger dehumidifier?
Basements tend to run cooler and damper than rooms above ground, so this calculator nudges the estimate up by about 10% when you mark the room as a basement.
Should I round up when choosing a unit?
Generally yes. A unit near the top of the suggested range runs less often, handles humid weather better, and tends to last longer than one that has to run flat out.
How do I confirm the right size?
Use this as a starting point, then cross-check with AHAM sizing guidance and the manufacturer's recommendations, taking your local climate and any moisture sources into account.
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