Fireproofing Calculator
Calculate spray-applied fireproofing material volume, weight, bag count, and cost for cementitious or fiber-type SFRM applications.
About this calculator
Steel Surface Area and Required Thickness are the two numbers that actually drive every quantity here -- material volume, weight, bag count, and cost all scale directly with each of them, since volume is simply area times thickness. The Fire Rating field, despite sitting right next to Required Thickness in the form, is purely a record for your submittal paperwork: it never enters the calculation, because in real practice the UL-listed assembly's Required Thickness (not the hour rating alone) is what a fireproofing contractor actually applies, and different UL systems can hit the same hour rating at different thicknesses depending on the steel's W/D ratio.
Fireproofing Type is a coded choice between cementitious SFRM (15 pcf density, $2.25/sq ft at 1 in) and mineral fiber SFRM (12 pcf, $3.00/sq ft at 1 in) -- at the default 1.5 in thickness on 5,000 sq ft, fiber ends up about 33% pricier overall ($22,500 vs $16,875) even though it weighs less per square foot, because its higher unit cost and lower per-bag coverage outweigh the density savings. The tool doesn't verify that your chosen thickness actually matches a real UL-listed assembly for the steel section and rating you need.
Inputs
Results
Fireproofing Weight
9,375 lbs
≈ 9 grand pianos
How to Use This Calculator
- Enter the total steel surface area in sq ft to be fireproofed (measure all exposed beam and column flanges and webs).
- Set the required thickness in inches from the UL-listed assembly (typically 0.5–3 in depending on W/D ratio).
- Note the fire resistance rating in hours (1, 2, 3, or 4) required by the building code for your records — the assembly's UL-listed Required Thickness above is what drives the material quantities, not this field.
- Select the fireproofing type: 1=cementitious SFRM or 2=mineral fiber SFRM.
- Read Bags Required and Coverage Rate to order materials; use Material Cost for budget planning.
- Note Labor Hours to schedule application crews — spray fireproofing is typically applied after structure is plumb and bolted.
How the result changes with Steel Surface Area
| Steel Surface Area | Fireproofing Weight |
|---|---|
| 2,500 | 4,688 lbs |
| 3,750 | 7,031 lbs |
| 7,500 | 14,063 lbs |
| 12,500 | 23,438 lbs |
What each input means
- Steel Surface Area
- Total surface area of steel members to be fireproofed.
- Required Thickness
- Required fireproofing thickness from UL listing (typically 0.5"-3").
- Fire Rating
- Required fire resistance rating in hours (1, 2, 3, or 4).
- Fireproofing Type
- Select fireproofing material type
What each result means
- Material Volume
- Total volume of fireproofing material required.
- Fireproofing Weight
- Total weight of applied fireproofing.
- Bags Required
- Estimated number of standard bags needed.
- Coverage Rate
- Effective coverage per bag at the specified thickness.
- Material Cost (est.)
- Estimated material cost based on type and thickness.
- Labor Hours (est.)
- Estimated application labor hours.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersSteel Surface Area = 5000, Required Thickness = 1.5, Fire Rating = 2, Fireproofing Type = 1 = 4 input(s) provided
- Calculate Fireproofing WeightFireproofing Weight = materialVolumeCf * density9375 = 9375
- Calculate Material VolumeMaterial Volume = surfaceArea * thicknessFt625 = 625
- Calculate Bags RequiredBags Required188 = 188
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Does changing the Fire Rating field change any of the calculated quantities?
No -- Fire Rating is declared as an input but never referenced inside the calculation. Every quantity (material volume, weight, bags, cost, labor hours) is driven entirely by Steel Surface Area, Required Thickness, and Fireproofing Type; Fire Rating is there purely for your own documentation.
Is mineral fiber fireproofing cheaper than cementitious SFRM?
Not in this calculator's default scenario -- at 5,000 sq ft and 1.5 in thickness, cementitious costs about $16,875 versus fiber's roughly $22,500, about a third more, even though fiber's lower 12 pcf density means less total weight applied to the steel.
What actually determines the fireproofing thickness I should enter?
Required Thickness should come from the UL-listed fireproofing assembly for your specific steel section and target fire-resistance rating, typically found in the UL Fire Resistance Directory -- this calculator takes that thickness as given rather than deriving it from the fire rating itself.
How does thickness affect coverage per bag?
Coverage Rate is inversely proportional to thickness -- at 0.5 in a bag covers about 80 sq ft, but at the maximum 4 in thickness that drops to only 10 sq ft per bag, since each bag holds a fixed volume that spreads thinner over more area at lower thicknesses.
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