Enter your job details below to get equipment recommendations based on IICRC S500 guidelines. This calculator helps restoration contractors properly size dehumidifiers, air movers, and air scrubbers for residential and commercial water damage projects.
Disclaimer: These recommendations are estimates based on IICRC S500 guidelines. Actual equipment needs may vary based on specific job conditions, moisture readings, and environmental factors. Always verify with moisture meters and adjust accordingly. For critical projects, consult with a certified restoration professional.
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How the Equipment Counts Are Calculated
The numbers come from IICRC S500, the standard restoration contractors bill against. Dehumidifiers: one LGR unit per 1,000 sq ft for a moderate loss, scaled up 50% for severe or Category 3 jobs. Air movers: one per 100–150 sq ft of wet floor, or one per 10–16 linear feet of wet wall. Air scrubbers only enter the count when containment is needed — mold, sewage, or any Category 3 water.
These are starting counts, not gospel. Moisture readings on day two tell you whether to pull equipment or add it. That's also why the disclaimer above matters: a calculator can't see your moisture map.
Frequently Asked Questions
How many air movers do I need per dehumidifier?
The working ratio is 4 air movers per dehumidifier. Air movers push moisture off wet surfaces into the air; the dehumidifier pulls it out. Run too many air movers without enough dehumidification and you just move humid air in circles — the structure stays wet.
How many dehumidifiers per square foot of water damage?
One LGR dehumidifier per 1,000 sq ft for a typical Category 1 or 2 loss with wet carpet and drywall. Severe losses or Category 3 water need roughly 1.5x that. A 2,500 sq ft severe loss means 4 LGR units running continuously, not 2.
What is the difference between Category 1, 2, and 3 water?
Category 1 is clean water from a supply line or rain. Category 2 ("grey water") carries contamination — washing machine discharge, toilet overflow with urine. Category 3 ("black water") is grossly contaminated: sewage, flooding from rivers, anything that sat for 48+ hours. Category 3 requires containment, HEPA air filtration, and disposal of porous materials.
When do I need air scrubbers on a water damage job?
Any time contamination is airborne or about to be: Category 3 water, visible mold, or demolition inside an occupied building. For standard clean-water drying, you usually don't need them. The calculator adds scrubbers automatically when you select Category 3 or mark containment as required.
Can I use a residential dehumidifier for restoration work?
It will pull some water, but a 50-pint home unit extracts a fraction of what an LGR does at restoration conditions and has no condensate pump, no hour meter, and no stacking frame. On a billable job, drying time is money — a $250 home unit that doubles the dry-out costs more than it saves.
What happens to drying equipment below 60°F?
Standard refrigerant dehumidifiers lose extraction fast below 60°F and can ice up entirely. Either heat the space to 70–80°F or switch to desiccant dehumidifiers, which keep working in cold conditions. The calculator switches its recommendation to desiccant when you select a cold environment.
Browse water damage restoration equipment — LGR dehumidifiers, air movers, and air scrubbers with prices listed. No quote required. Sizing a specific dehumidifier? Use the dehumidifier sizing calculator.