Industrial Coating Spec Calculator

Industrial coating specs are written in terms of dry film thickness (DFT) — the thickness of the cured coating — but applicators need to know wet film thickness (WFT), the thickness of the coating as it goes on before solvent flashes off and solids consolidate. This calculator derives WFT with the standard relationship WFT = DFT ÷ (percent solids by volume ÷ 100): if a coating is only 50% solids, you need to apply twice as much wet material as the target dry thickness implies, since half of what you spray evaporates away. Theoretical coverage (typically 1604 sq ft/gallon at 1 mil, the standard constant derived from one gallon spread to 1 mil over one square foot) is scaled down by percent solids and by the target DFT to get real theoretical coverage at your specified thickness, then reduced further by your waste factor — material lost to overspray, drips, and surface irregularities, typically 15-30% depending on application method — to arrive at practical coverage.

Material needed is simply surface area divided by practical coverage, rounded up to whole gallons for ordering. Coats required is a separate check based on the assumption that no single coat should exceed 10 mils DFT (thicker single coats risk solvent entrapment, sagging, and cracking during cure), so specs calling for more than 10 mils dry are automatically split into multiple coats. A key assumption: this calculator treats waste factor as a flat percentage applied uniformly across the whole job, when in practice spray application on complex geometry can waste significantly more material than a flat rate captures — pad your gallon order accordingly on jobs with lots of edges, corners, or overhead work.