Dehumidifier Sizing Calculator
Find out what size dehumidifier you need. Enter your room size and how wet it is to get the moisture-removal capacity (pints per day) and the number of LGR units for the job.
For a water loss, a dehumidifier needs roughly 0.06–0.15 AHAM pints per day per square foot, depending on how wet it is. A 1,000 sq ft wet area needs about 90 PPD — one 130-pint LGR. Restoration Equipment Supply’s calculator below sizes it and counts the units.
- Desiccant Dehumidifiers
- LGR Dehumidifiers
- Air Movers
- HEPA Air Scrubbers
- Portable Air Scrubbers
- Negative Air Machines
- HEPA Vacuums
- Generators
Your Result
Estimate for planning. We confirm the exact package with you — rental or purchase.
About This Calculator
A dehumidifier sizing calculator estimates how many pints of water per day you must remove to dry a space, then how many units that takes. Wetter conditions and larger areas need more capacity. Restoration jobs run wetter than everyday humidity control, so we size to the loss, not to a comfort setting.
Is this dehumidifier sizing calculator accurate?
It gives a solid planning estimate using square-footage dampness factors and the IICRC S500 approach of sizing on AHAM-rated pints per day. For a job we always confirm the exact equipment with you by phone before delivery.
Can I rent or buy the equipment?
Both. Restoration Equipment Supply rents and sells the full drying and power fleet across NJ, NY, CT, PA, NC, SC and Florida, with same-day delivery for emergencies. Browse the full catalog →
What other calculators do you have?
Use our equipment sizing calculator, generator sizing calculator, and the tools in the Calculators menu to build a complete package.
24/7 Emergency Dispatch
Water on the Floor
Right Now?
Same-day emergency delivery. A real person answers, never a machine.
(973) 685-4030- Dispatch 24/7
- Same-Day Emergency Delivery
- Delivered, Set & Monitored
What Size Dehumidifier Do I Need?
Multiply the wet area by a dampness factor to get the AHAM pints per day you need to remove, then divide by your unit’s AHAM rating. That is the whole calculation this tool runs.
The dehumidifier sizing formula
Pints per day needed = affected sq ft × dampness factor. Units = pints per day ÷ unit AHAM rating, rounded up. The factors are 0.06 (damp), 0.09 (wet), 0.12 (very wet) and 0.15 (saturated / flood).
| Wet area | Damp (0.06) | Wet (0.09) | Very wet (0.12) | Saturated (0.15) |
|---|---|---|---|---|
| 300 sq ft | 18 PPD | 27 PPD | 36 PPD | 45 PPD |
| 600 sq ft | 36 PPD | 54 PPD | 72 PPD | 90 PPD |
| 1,000 sq ft | 60 PPD | 90 PPD | 120 PPD | 150 PPD |
| 2,000 sq ft | 120 PPD | 180 PPD | 240 PPD | 300 PPD |
Worked example
A 1,000 sq ft finished basement that is “wet”: 1,000 × 0.09 = 90 PPD. One LGR rated 130 pints/day AHAM covers it (90 ÷ 130 = 0.7 → 1 unit). If the same basement is saturated, 1,000 × 0.15 = 150 PPD → 2 units.
The IICRC volume method
Professional drying plans under IICRC S500 size by chamber volume instead: PPD = cubic feet ÷ class factor (LGR: 100, 50, 40, 40 for Classes 1–4). A 30 × 20 × 8 ft Class 2 room is 4,800 ft³ ÷ 50 = 96 PPD. Run that method, plus air movers and desiccant CFM, in the full IICRC equipment calculator.
AHAM rating vs. saturation rating
Always size on the AHAM rating, measured at 80°F and 60% relative humidity. Saturation ratings (near 90°F / 90% RH) look bigger on a spec sheet but overstate what a unit removes as the space dries. For large or cold losses, a desiccant dehumidifier outperforms refrigerant units; for most rooms, an LGR dehumidifier rental is the right tool.
What size dehumidifier do I need for 1,000 square feet?
For a wet 1,000 sq ft area, about 90 AHAM pints per day — one 130-pint LGR. Damp areas need about 60 PPD; saturated areas about 150 PPD.
How do you calculate dehumidifier size?
Multiply the wet square footage by a dampness factor (0.06–0.15) to get pints per day, then divide by the unit’s AHAM rating and round up. Restoration pros also use cubic feet ÷ IICRC class factor.
What size dehumidifier do I need for a flooded basement?
Use the saturated factor: sq ft × 0.15. A 1,500 sq ft flooded basement needs about 225 PPD — two 130-pint LGRs, or a desiccant for cold or very large spaces.
Is an LGR better than a conventional dehumidifier?
For water damage, yes. LGR (low-grain refrigerant) units keep removing water as the air gets drier, where conventional units stall. IICRC factors let one LGR cover more cubic feet per pint than a conventional unit in Class 2 and 3 losses.
Updated October 2026 · Reviewed by the Restoration Equipment Supply dispatch team
How Our Dehumidifier Sizing Calculator Works
Dehumidifier sizing calculator is sized to the job by our dispatch team, so you rent what the loss needs and nothing extra.
Get Your Free
Quote
Tell us the job and we'll stage the right package. A real person answers, any hour.
📞 (973) 685-4030Get a Quote
Fast response, 24/7.