Free calculator

Dehumidifier Sizing Calculator

Estimate the dehumidification a space needs for water-damage drying. Enter the room's cubic footage and the class of loss to get a target in AHAM pints per day — and roughly how many LGR units that means.

An initial-setup estimate using the cubic-foot method. Confirm against your dehumidifier's rated performance and your daily readings.
Get the printable worksheet
Target dehumidification
AHAM pints / day
Room volume
Class factor
LGR units (approx.)

Drying Equipment Worksheet

Fill this in on site and attach it to your file.

FieldValue
Job / claim # 
Room / area 
Target PPD 
Dehumidifier(s) placed 
Air movers placed 
Class of loss 
Day 1 / 2 / 3 RH 

How dehumidifier sizing works

This calculator uses the cubic-foot method: take the room's volume (length × width × height) and divide by a factor that tightens as the class of loss rises. The result is a target in AHAM pints per day — the standardized way dehumidifier capacity is rated — which you then translate into units.

Class factors (assumptions, LGR)

ClassDivide cubic feet by
Class 1100
Class 250
Class 340
Class 440 (specialty)

Manufacturers rate LGR dehumidifiers at AHAM (a fixed test condition) and at higher "saturation" pints. Real capacity drops as the air dries, so size with headroom and let your daily readings drive the adjustments.

Reference only. Vigilince makes no compliance claim — final equipment decisions are the professional's, verified on site.
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