🎨 Paint Coverage Calculator
Enter a coating's volume solids, target dry film thickness, and a loss factor to see both the theoretical and practical spreading rate in square metres per litre — the figure to budget paint against.
🎨 Calculate Spreading Rate
What is a Paint Coverage Calculator?
It works out how far a litre of a marine coating actually goes. From the paint's volume solids and the dry film thickness you're aiming for, it derives the theoretical spreading rate, then applies a loss factor for overspray and waste to give the practical coverage you can rely on.
Coverage is the link between a coating's data sheet and the number of tins on your bill. Use this to compare products fairly, plan how many coats a litre buys you, and feed an honest coverage figure into your antifouling and paint-cost estimates.
❓ Frequently Asked Questions
How is paint coverage calculated?
Theoretical coverage in square metres per litre equals the volume solids percentage times ten, divided by the target dry film thickness in microns. Higher solids or a thinner film stretch a litre further; a thicker specified film covers less. This calculator applies that formula and then discounts it for real-world losses.
What is the difference between theoretical and practical coverage?
Theoretical coverage assumes every drop of paint ends up on the hull at exactly the specified thickness. In practice you lose paint to overspray, uneven surfaces, roller absorption, and drips. The loss factor knocks a percentage off the theoretical figure to give a practical coverage you can safely budget paint against.
What loss factor should I use?
It depends on the method and conditions. Brushing and rolling on a smooth hull might lose only 10–20%, while spraying, rough surfaces, or awkward shapes can push losses to 30–50% or more. If you're unsure, start around 20–30% for rolling and adjust from experience on your own boat.
How does coverage relate to how much paint I buy?
Divide the area you need to coat by the practical coverage to get litres per coat, then multiply by the number of coats. That's exactly what the antifouling and paint-cost calculators do — this tool gives you the reliable coverage figure to feed into them so the order comes out right.