Water Damage Calculator
Estimates the water you are dealing with, the IICRC category and class, the air movers and dehumidification the job needs, how long drying realistically takes, and what professional mitigation costs in the US.
Quick answer
62.3 gallons (8.3 ft³) across 200 ft² — a Class 2, Category 1 loss. Expect roughly 4-5 air movers and 32 pints/day of LGR dehumidification, with an estimated 3-5 day dry-down and $600-$800 of professional mitigation.
Why Class 2: 5-40% of the affected materials are wet. Drying days are an industry rule of thumb — IICRC S500 sets no fixed duration; equipment comes out when materials reach a measured dry standard.
The affected area
Estimated professional mitigation
$600 – $800
Class 2 · Category 1 · 3-5 days of drying · typical Class 2 project $500-$1,000
Water, drying load and equipment
- Standing water
- 62.3 gal (8.3 ft³)
- Extractor dumps (≈15 gal tank)
- ≈ 5
- IICRC class
- Class 2
- Drying chamber volume
- 1,600 ft³
- Air movers (IICRC method)
- 4-5
- Dehumidification, LGR
- 32 pints/day
- Drying time (rule of thumb)
- 3-5 days
Equipment sizing follows the IICRC worksheets: one air mover per affected room, one per 70-50 ft² of wet floor, one per 150-100 ft² of wet wall above 2 ft, plus one per inset over 18 in. Dehumidification is chamber cubic feet ÷ 50 for Class 2 with LGR (conventional refrigerant: 40 pints/day).
What usually has to go
- Carpet: can be dried in place if drying starts immediately
- Carpet pad: always removed — it cannot be dried in place against the subfloor
- Drywall: dryable in place only if wicking stays under 24 in
- Hardwood: may be saved with specialty drying
Estimates, not a quote
Costs are US national averages (2025-2026 marketplace data) and vary by ±40% or more by region, contractor and insurer. Only a certified restorer can classify a loss, and most insurers will not accept a self-assessed category or class. If the water is Category 2 or 3, if mold is already visible, or if you cannot find the source, call a professional today.
How this calculator works
- Standing water = area × depth × 0.62333 gallons per square foot per inch (7.48 gallons per cubic foot ÷ 12).
- Class comes from how much material is saturated and what absorbed it: under 5% is Class 1, 5-40% is Class 2, over 40% or an inch of standing water or multiple levels is Class 3, and any significant wetting of low-evaporation materials (hardwood, slab, crawlspace soil, multilayer assemblies) is Class 4 specialty drying.
- Air movers use the IICRC worksheet method, and dehumidification uses the IICRC factor chart applied to the drying chamber volume: Class 1 ÷100, Class 2 ÷50, Class 3 ÷40, Class 4 ÷40 for LGR.
- Drying time is shown as an industry rule-of-thumb band (Class 1 2-3 days, Class 2 3-5, Class 3 4-7, Class 4 7-14+). The standard does not publish durations: it requires daily monitoring until materials reach a measured dry standard, which is why "3 day drying" is a myth.
- Mitigation cost uses US-average per-square-foot rates by category (Cat 1 $3-4, Cat 2 $4-6.50, Cat 3 $7-7.50) and excludes replacing flooring or contents.
Not a substitute for an on-site assessment: hidden moisture behind walls and under floors is what turns a small leak into a mold claim. A moisture meter and thermal camera reading is the only way to confirm the dry standard was met.
About This Calculator
Estimate standing water volume, the IICRC water category and class, how many air movers and how much LGR dehumidification a wet area needs, how long drying realistically takes, and what professional mitigation costs in the US. Uses the IICRC air mover and dehumidification worksheets and EPA mold-prevention guidance.
Frequently Asked Questions
How long does it take to dry out water damage?
Industry rule-of-thumb bands are Class 1 about 2-3 days, Class 2 about 3-5 days, Class 3 about 4-7 days and Class 4 about 7-14 days or longer.
Those numbers are not published in ANSI/IICRC S500. The standard requires drying to a measured "dry standard" with daily monitoring of moisture content, and equipment is removed when materials reach that reading, not on a calendar date. This is why the industry saying "three-day drying is a myth" exists. Any calculator that promises a fixed number of days is quoting convention, not the standard.
How many gallons of water is one inch of water in my basement?
One square foot covered by one inch of water is 0.623 gallons. The exact conversion is 7.48 gallons per cubic foot, divided by 12 inches: 1,000 sq ft at one inch deep is about 623 gallons.
To estimate standing water: area (sq ft) x depth (inches) x 0.623. A 200 sq ft room with half an inch of water holds about 62 gallons. Note this measures free-standing water only, not the much larger volume held inside carpet, pad and drywall.
How many air movers do I need for water damage?
The IICRC worksheet method is four steps: one air mover in every affected room; one per 50-70 sq ft of affected wet floor; one per 100-150 sq ft of wet wall or ceiling above two feet; plus one for every wall inset or offset deeper than 18 inches, with every fraction rounded up.
Example: a 200 sq ft carpeted room is 1 (room) + 3-4 (floor) = 4-5 air movers. Air movers must run continuously across all wet surfaces, angled 5-45 degrees with the outlet near the wall, and placement should be checked no later than the following day.
What size dehumidifier do I need for water damage?
The IICRC dehumidification chart divides the drying chamber volume in cubic feet by a class factor to get total pints per day (PPD). For low-grain refrigerant (LGR) units the factors are Class 1 divide by 100, Class 2 divide by 50, Class 3 divide by 40 and Class 4 divide by 40.
Example: a 200 sq ft room with an 8 ft ceiling is 1,600 cubic feet; Class 2 gives 1,600 / 50 = 32 PPD. Then divide by the unit's AHAM-rated capacity to get the number of units, rounding up. Conventional refrigerant dehumidifiers are not rated for Class 4 losses - those need LGR or desiccant equipment.
What is the difference between Category 1, 2 and 3 water damage?
Category describes how contaminated the water is. Category 1 is clean water from a sanitary source: burst supply lines, a clean appliance, rain that has not pooled. Category 2 is grey water with significant contamination: washing machine or dishwasher discharge, toilet overflow containing urine only, aquarium water, groundwater seepage. Category 3 is black water that is grossly contaminated: sewage backup, floodwater, or water containing feces.
Category can only escalate, never de-escalate: clean water sitting 24-48 hours becomes Category 2, and past 72 hours in warm conditions it is treated as Category 3. Category 2 requires EPA-registered antimicrobial treatment and removal of porous materials that cannot be cleaned; with Category 3, all porous materials that contacted the water must be removed regardless of how they look.
What is the difference between Class 1, 2, 3 and 4 water damage?
Class describes how much material absorbed water and therefore how much evaporation the drying equipment must handle. In the current S500 wording: Class 1 is under 5% of porous materials affected, Class 2 is 5-40%, and Class 3 is more than 40%. Class 4 is defined differently: any significant absorption into low-evaporation materials or assemblies, such as hardwood, plaster, concrete, masonry, multilayer wallboard or multilayer subfloors.
Class 4 is the most under-diagnosed condition in the field. It needs specialty drying - floor mats, injection drying or containment - longer time, and LGR or desiccant dehumidification. If hardwood, a concrete slab or crawlspace soil is wet, treat it as Class 4 and get an on-site assessment.
How fast does mold grow after water damage?
The EPA guidance is to dry water-damaged areas and items within 24-48 hours to prevent mold growth: if wet materials are dried inside that window, mold usually will not grow.
Keep indoor relative humidity below 60% and ideally 30-50%. Under about 10 sq ft of mold is generally a DIY cleanup, but larger areas or significant water damage should be handled by a professional. Biocides are not recommended as routine practice, dead mold can still cause allergic reactions, and porous materials such as ceiling tile and carpet often have to be discarded rather than cleaned.
Does homeowners insurance cover water damage?
Sudden and accidental damage is normally covered: burst or frozen pipes, accidental plumbing leaks, appliance failures, and overflow from a clogged sink, tub or toilet. Gradual leaks, long-term corrosion, neglect, mold from unresolved moisture, rising floodwater and sewer backup are normally excluded - flood needs a separate policy and sewer backup usually needs an endorsement.
Many policies cap mold coverage around $10,000. Every policy also imposes a duty to mitigate: report the loss promptly, photograph everything before cleanup, remove standing water, dry the area, keep every receipt, and make temporary repairs. Failing to mitigate is one of the most common reasons a legitimate claim gets reduced.
The SuperCalc Editorial Team maintains calculator interfaces, formula notes, examples, and supporting explanations. Methods, assumptions, source links, and review depth vary by calculator and are documented on the relevant page where available.