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Calcimator

Intumescent Coating Calculator

Calculate intumescent fire protection coating DFT and quantity from steel section factor, fire rating, and critical temperature.

Inputs

%
%

Results

Required DFT (µm)

250

Coats required

1

Required WFT (µm)368
Theoretical volume (L)36.76
Practical volume (L)42.28
Coverage rate (m²/L)2.72
Coating weight (kg)55
How to Use This Calculator
  1. Enter structural steel section: profile type (I-beam, column, hollow section) and section factor (Hp/A in m-1).
  2. Enter required fire resistance rating (minutes: 30, 60, 90, 120) and design temperature (°C).
  3. Read required intumescent dry film thickness (mm) for the specified fire resistance period.
  4. Select intumescent product and verify the manufacturer's DFT table matches the calculated requirement.
  5. Apply in multiple coats if required DFT exceeds the maximum single-coat thickness in the product data sheet.

What each input means

Section factor Hp/A (m⁻¹)
Heated perimeter / cross-section area. Higher = thinner steel, more coating. Typical: 50–350 m⁻¹.
Fire rating (minutes)
Required fire resistance period: 30, 60, 90, or 120 minutes.
Critical temperature (°C)
Steel limiting temperature. Beams: 550°C, columns: 620°C (load ratio dependent).
Steel surface area (m²)
Total surface area of steel to be coated.
Volume solids (%)
From product TDS. Thin-film intumescents: 60–75%.
Waste factor (%)
Allowance for complex steelwork, bolts, edges. Typically 10–20%.

What each result means

Required DFT (µm)
Dry film thickness per manufacturer guidelines for the section factor and fire rating.
Required WFT (µm)
Wet film thickness to achieve the target DFT.
Coats required
Number of application coats (max ~650 µm WFT per coat).
Theoretical volume (L)
Paint volume with zero waste.
Practical volume (L)
Including waste factor for complex steelwork.
Coverage rate (m²/L)
Spreading rate at the calculated DFT.
Coating weight (kg)
Estimated weight at ~1.3 kg/L coating density.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Section factor Hp/A (m⁻¹) = 160, Fire rating (minutes) = 60, Critical temperature (°C) = 550, Steel surface area (m²) = 100 = 6 input(s) provided
  2. Calculate Required DFT
    Required DFT = max(250, min(6000, dft))
    250 = 250
  3. Calculate Coats required
    Coats required
    1 = 1
  4. Calculate Required WFT
    Required WFT = dftClamped / (volumeSolids / 100)
    368 = 368
  5. Calculate Theoretical volume
    Theoretical volume = surfaceArea * dftClamped / (volumeSolids / 100 * 1000)
    36.76 = 36.76

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