Antifouling Paint Estimator
Estimate how much antifoul paint you need, how many cans to buy, and your likely total cost.
What this antifoul calculator does
This tool helps boat owners estimate antifouling paint requirements before haul-out season. It takes your hull dimensions (or measured wetted area), the number of coats, paint coverage rate, and expected wastage to produce a practical shopping estimate: total liters, number of cans, and budget.
How the math works
1) Estimate wetted surface area
If no measured area is provided, the calculator uses a geometry-based estimate:
Different hull forms carry different coefficients. For most cruising sailboats, 0.85 is a reasonable starting point.
2) Account for coats and wastage
Wastage includes roller loss, tray retention, extra loading around high-wear zones, and small touch-up jobs.
3) Convert area to liters and cans
Cans Needed = round up(Liters Needed ÷ Can Size)
The result rounds up to whole cans so you do not run short halfway through the job.
Tips for better antifoul estimates
- Use actual product data sheets; coverage varies by brand and formula.
- Increase wastage for first-time DIY application or rough surfaces.
- Add an extra stripe coat at the waterline, bow, and leading edges.
- If you sand heavily, primer or tie-coat may change your total volume needs.
- Always check minimum and maximum overcoating intervals in the technical sheet.
Choosing antifouling paint type
Hard antifoul
Durable coating that can be scrubbed. Often preferred for faster boats, trailers, or frequent cleaning schedules.
Ablative (self-polishing) antifoul
Gradually wears away to expose fresh biocide. Popular for cruising boats because it reduces paint buildup over time.
Hybrid systems
Some products blend durability and controlled polishing. Good choice when you want a balance of service life and smooth finish.
Common planning mistakes to avoid
- Buying exactly the theoretical liters with no safety margin.
- Ignoring local fouling intensity and water temperature.
- Mixing incompatible paint chemistries without a tie-coat.
- Not stirring paint fully; active ingredients settle quickly.
- Applying too thickly in one pass instead of using proper coat count.
Example scenario
A 10.5 m cruising sailboat with 3.4 m beam and 1.8 m draft, two coats, 10 m²/L coverage, 10% wastage, and 2.5 L cans at $89 each gives an estimate close to: around 9 liters, or 4 cans, for a total budget near $356.
Final note
This calculator is an estimate tool for planning and budget control. For final purchase decisions, prioritize manufacturer guidance, yard experience, and your local fouling conditions.