Paint Spreading Rate Calculator
Calculate theoretical and practical coverage for coatings
Solid content percentage of the paint
Desired Dry Film Thickness
Area to be painted in square meters
Wastage due to spray, wind, or surface profile (typically 20-40%)
Optional: Calculate total material cost
Theoretical Spreading Rate:
– m²/L
Practical Spreading Rate (Estimated):
– m²/L
Wet Film Thickness (WFT):
– microns
Total Paint Required:
– Liters
Estimated Material Cost:
–
Understanding Paint Spreading Rate
The spreading rate of a coating determines how much area a specific volume of liquid paint can cover at a desired thickness. Accurate calculation of the spreading rate is crucial for project estimation, budgeting, and ensuring the durability of the protective coating system.
Key Formula:
Theoretical Spreading Rate (m²/L) = (Volume Solids % × 10) / Dry Film Thickness (µm)
Theoretical Spreading Rate (m²/L) = (Volume Solids % × 10) / Dry Film Thickness (µm)
Theoretical vs. Practical Spreading Rate
Theoretical Spreading Rate (TSR) assumes a perfectly flat surface and zero wastage. It is calculated based strictly on the volume solids of the paint and the target dry film thickness (DFT).
Practical Spreading Rate (PSR) accounts for real-world factors. In any painting application, paint is lost due to surface roughness (dead volume), application method (spray, roller, brush), wind drift, and spills. This is known as the "Loss Factor."
Inputs Explained
- Volume Solids (%): The percentage of the paint mixture that remains on the surface after the solvents have evaporated. Higher solids mean better coverage.
- Target DFT (Microns): The required thickness of the cured paint film. 1000 microns = 1 mm.
- Loss Factor (%): An estimation of paint waste. Airless spray application typically incurs 30-40% loss, while rolling might incur 10-20%.
Calculating Wet Film Thickness (WFT)
Painters measure thickness while the paint is still wet using a WFT gauge. Knowing the required WFT ensures that when the paint dries (and solvents evaporate), the remaining film meets the target DFT.
WFT (µm) = (DFT × 100) / Volume Solids %