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How do you convert WFT to DFT?

DFT = WFT × % Volume Solids / 100. For example, if WFT is 200 µm and volume solids is 65%, DFT = 200 × 65 / 100 = 130 µm.

What is the theoretical coverage formula for paint?

Theoretical Coverage (m²/L) = (10 × % Volume Solids) / DFT (µm). This gives the maximum area one liter of paint can cover at the specified dry film thickness, assuming no losses.

What is a typical volume solids percentage for industrial coatings?

Epoxy primers typically have 50-65% volume solids, while zinc-rich primers range from 40-55%. Polyurethane topcoats are often 50-60%. Always check the Product Data Sheet (PDS) for the exact value.

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WFT ↔ DFT Paint Coverage Calculator

Wet-to-dry film thickness per NACE / AMPP / BGAS

Volume Solids (%)

Wet Film Thickness, WFT (µm)

Dry Film Thickness, DFT (µm) — optional

Surface Area (m²) — optional

Practical Application

Coating inspectors use this math on site daily to verify painters are applying adequate wet film thickness. Use a wet film gauge (comb-type) immediately after application, then compare with the calculated DFT to ensure compliance with the specified NACE/AMPP coating system.

Loss Factors

Theoretical coverage assumes zero loss. In practice, apply a loss factor of 20-40% depending on application method (airless spray, brush, roller), surface profile, and environmental conditions. Consult SSPC-PA 2 for measurement procedures.

The WFT-to-DFT calculator is the most-used tool by coating inspectors on site. It converts wet film thickness (measured with a comb gauge immediately after application) to dry film thickness, calculates theoretical paint coverage, and estimates total paint consumption for a given surface area. Understanding this math is essential for NACE/AMPP/BGAS-CSWIP coating inspectors and QA/QC engineers.

How WFT and DFT Relate

When paint is applied, the wet film contains solvent or water that evaporates as it dries. The dry film thickness is always less than the wet film thickness. The ratio depends on the volume solids percentage of the coating. A coating with 65% volume solids means that 65% of the wet volume remains as solid film after drying. The relationship is simple: DFT = WFT × (% Volume Solids / 100).

Using the Calculator on Site

Find the volume solids on the Product Data Sheet (PDS) for the specific coating system.
Measure the wet film thickness with a wet film gauge (comb-type) immediately after application.
Enter the WFT and volume solids to calculate the expected DFT.
After curing, verify the actual DFT with a dry film thickness gauge per SSPC-PA 2.
Use the coverage and consumption fields to estimate paint quantity for the full job.

Theoretical vs Practical Coverage

Theoretical coverage assumes zero loss — no overspray, no material left in the pot, no surface profile effect. In practice, apply a loss factor of 20–40% depending on the application method. Airless spray on a complex surface with high profile typically loses 30%. Brush and roller application loses less (10–15%) but is slower. Always order more paint than the theoretical calculation suggests.

Common Coating System DFT Ranges

Zinc-rich primer: 50–75 µm DFT (typical volume solids: 45–55%)
Epoxy intermediate coat: 100–150 µm DFT (typical volume solids: 55–70%)
Polyurethane topcoat: 50–75 µm DFT (typical volume solids: 50–60%)
Glass flake epoxy: 500–1000 µm DFT (typical volume solids: 70–85%)

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