Structural Drying Equipment Calculator
Work out roughly how many air movers and LGR dehumidifiers you need to dry a room, from the affected floor area and labeled IICRC/AHAM coverage typicals you can adjust.
Calculator
Drying 500 sq ft takes roughly 9 air movers (about one per 60 sq ft) and 1 LGR dehumidifier (about one per 500 sq ft). These are IICRC/AHAM planning typicals — the class of water, materials and airflow change the real count, so a certified technician must confirm the drying plan.
Structural drying uses two machines working together: air movers push a high-velocity sheet of air across wet surfaces so moisture evaporates, and LGR (low-grain refrigerant) dehumidifiers pull that moisture back out of the air so it does not just resettle. Under-size either and the structure never dries; over-size and you are paying for equipment days you do not need. The IICRC and AHAM publish coverage rules of thumb you can start from and adjust for the class of water.
Formula
air_movers = ceil(affected_sqft ÷ sqft_per_mover)
dehumidifiers = ceil(affected_sqft ÷ lgr_sqft)
Both round up, because you deploy whole machines — a fractional unit still means one more on the floor.
Worked example
500 sq ft at 60 sq ft per air mover and 500 sq ft per LGR:
air movers = ceil(500 ÷ 60) = ceil(8.33) = 9
dehumidifiers = ceil(500 ÷ 500) = 1 LGR
So a 500 sq ft room needs roughly 9 air movers and 1 LGR dehumidifier. A perimeter-based rule (about one air mover every 10–16 linear ft of wet wall) is the common alternative for wicked-up walls.
These are planning typicals, not a drying plan
Coverage numbers are labeled IICRC/AHAM rules of thumb. The real count depends on the class of water (a Class 3 overhead soak needs more than a Class 1 spill), the materials (hardwood and plaster hold water far longer than carpet), and the airflow geometry of the room. A certified technician places equipment, monitors moisture daily and adjusts until the materials hit dry standard — that on-site plan is what actually governs the job.
Air movers evaporate; dehumidifiers capture. Running air movers without enough dehumidification just moves wet air around and can spread moisture into dry areas, so keep the two in balance.
Reference table
Labeled IICRC/AHAM rules of thumb for structural drying. A certified technician confirms the real count from the class of water, materials and airflow on site.
| Equipment | Typical coverage |
|---|---|
| Air mover (by floor area) | ~60 sq ft each (range ~50–70) |
| Air mover (by wall perimeter) | ~14 linear ft each (range ~10–16) |
| LGR dehumidifier | ~500 sq ft each (Class 2) |