SettingsSettings for this calculationUS
The total steel surface area to be coated.
Include all exposed faces of the steel member(s) that require fireproofing, not just the footprint.
The cured coating thickness required for the specified fire-resistance rating.
This value comes from the manufacturer's UL-listed DFT tables for your steel section's size factor (Hp/A) and target rating.
The percentage of the wet coating that remains as solid film after cure.
Higher solids content means less shrinkage from wet to dry film, so less wet material is needed for the same dry thickness.
Intumescent coating volume needed
9.57 gal
The dry film thickness required for a specific fire-resistance rating depends on the steel section's size factor (Hp/A) and is set by the manufacturer's UL-listed DFT tables for your exact rating and steel profile — this calculator only converts a DFT you already know into material volume, it does not determine the required DFT itself.
- Required wet film thickness
- 35.71 mils
They open the calculator with your figures already in it
Intumescent Fireproof Coating Volume Calculator: 9.57 gal — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Wet film thickness = target dry film thickness ÷ product solids content; material volume = steel surface area × wet film thickness — the same wet/dry film relationship used for any solvent/water-based coating
Inputs used
- Steel Surface Area
- 430 sq ft
- Target Dry Film Thickness (mils)
- 25
- Product Solids Content (%)
- 70
Intermediate steps
- Required wet film thickness
- 35.71 mils
Confidence note: The dry film thickness required for a specific fire-resistance rating depends on the steel section's size factor (Hp/A) and is set by the manufacturer's UL-listed DFT tables for your exact rating and steel profile — this calculator only converts a DFT you already know into material volume, it does not determine the required DFT itself.
What this calculation does not cover
- The solids figure has to be solids BY VOLUME, and data sheets print solids by weight right beside it. On a heavily filled intumescent the weight figure runs well above the volume figure — a product quoted at 78% by weight can be near 65% by volume — and entering the higher one understates the wet material by that same margin, on a coating whose whole job is to reach a listed dry thickness.
- Theoretical volume, with nothing lost between the pot and the steel. Spraying open sections — web, both faces of every flange, edges — throws a large share of the material straight past the member, and applicators deliberately overapply on top of that because gauge readings have to meet a MINIMUM everywhere rather than an average. Both push the quantity actually ordered well above this number.
- Covers the intumescent film alone. The system that carries the fire test is a specified primer, the intumescent, and usually a sealer or decorative topcoat, each with its own coverage rate and its own compatibility restrictions — a rated build-up is not the intumescent on its own, and a topcoat chosen for colour rather than from the listing can stop the film expanding.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Part of a bigger job
This trade is one line of a job takeoff. Run the whole job and every other trade comes back with it, off the same measurements.
also measures11 other trades
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Wet film thickness = target dry film thickness ÷ product solids content; material volume = steel surface area × wet film thickness — the same wet/dry film relationship used for any solvent/water-based coating
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Your workspace
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Tools and safety for this job
To roll and cut in two coats and fire-protect the new steelwork. Generic types, no brands, no prices.
Protection this work requires
- Joint-compound dust is very fine and travels: a P1/FFP1 mask is the minimum, and a damp-sponge finish avoids most of it.
- A dust mask does nothing about solvent vapour: ventilate through, and use an organic-vapour (A1) cartridge respirator in an enclosed room.
- Most fatal falls on small jobs are from under three metres: use a tower or a ladder tied at the top, and never work off the top two rungs.
- Knives cause more site injuries than any power tool: cut away from your body, change blades often, and wear cut-resistant gloves to EN 388 level C for repeated cutting.
Fire-protect the new steelwork: The period of fire resistance a steel needs, and whether a given board or coating gives it at that section's size, come from the building-control drawings and the product's test data. This site does not certify fire protection or say which period applies.
Show the 8 tools this job needsHide tools
Essential
Brushes
Drywall screw gun
Dust sheets and masking
Roller frame, sleeves and tray
Tape measure
Utility knife
Recommended
Extension pole
Step ladder
Also needed as materials: masking tape, plastic sheeting, replacement blades, roller sleeves.
what each painting tool is for and what each fire-protection tool is for, and the spec that decides which to buy where one does.