Size air movers and dehumidification for a structural dry-out using the IICRC S500 method. Enter the room, the water class, and the category, and the tool returns equipment counts with an S500-referenced justification you can put in the estimate and bill in Xactimate.
Two numbers drive a water loss, and they answer different questions. The class tells you how much drying equipment the room needs. The category tells you how much of the room has to come out. Get both right and the estimate holds up.
Class is the evaporation load. Class 1 is a small wet area with low-permeance material and little to dry. Class 2 is a whole room with water wicked up the wall under 24 inches, the everyday supply-line or dishwasher loss. Class 3 is water that came from above, so the ceiling and the full height of the walls are saturated and the count of drying equipment climbs. Class 4 is bound water trapped in hardwood, plaster, lath, or concrete, which needs specialty low-humidity drying and the most time. When people search for water damage class 2 drying equipment, this is the axis they mean: more class, more air movers and dehumidifiers.
Category is contamination, and it decides scope. Category 1 is clean water from a broken supply line. Category 2 is gray water from an appliance discharge or a toilet overflow with no solids. Category 3 water is grossly contaminated: sewage backups, rising ground water, and wind-driven flood water from outside. A category 3 loss is not a dry in place job. The porous materials that soaked it up get removed, the cavity is cleaned and treated, and containment holds the line while the work happens, so the scope grows well past the drying setup. Time also matters here, because clean water left standing degrades to a higher category, and a category 1 loss that sat over a weekend is documented and scoped as category 2.
AI Estimate Assistant, from Antero Trail, turns field notes, photos, and floor plans into carrier-ready Xactimate estimates. The calculator on this page is one piece of that engine, pulled out and made free. In the app, the drying setup writes itself from the flood intake. Rooms, classes, and per-day WTR equipment lines land in the estimate automatically.
The tool follows the IICRC S500 drying method. Air movers are sized from the affected area and the water class, because the class describes how much of the room is wet and how fast it will give up water. As a working baseline the S500 references roughly one air mover for the first wet wall in a room plus one for each additional wall, and adds a unit for each offset, inset, or closet that would otherwise sit in dead air. Higher classes and wet ceilings raise the count because there is more surface evaporating at once.
Dehumidification is sized from the volume of the wet space and the class, then divided by the pints-per-day rating of the units you plan to run. The category of water changes the scope rather than the airflow: category 2 and category 3 losses bring containment, antimicrobial application, and removal of porous materials that cannot be cleaned, and the tool flags those so they are not left out of the estimate. Every count is a starting point that a technician confirms against daily moisture readings, which is exactly how S500 expects drying to be documented.
These calculators produce planning estimates from published public rate schedules. They are not a formal quote. Confirm equipment, access, and pricing with a licensed operator or rental yard before you rely on any number for an estimate.