Bottom Paint Calculator 🎨
Calculate how much bottom paint you need for your boat. Enter waterline length, beam, hull type, and number of coats.
How to Use the Bottom Paint Calculator
Enter waterline length, beam, and hull type to calculate wetted surface area and paint needed.
V-hull: L×B×0.85, flat bottom: L×B×0.75, round bottom: L×B×0.90 for wetted area.
One gallon of paint covers approximately 375 square feet. Total paint is determined by number of coats.
FAQ
How do I calculate how much bottom paint I need?
Wetted surface area varies by hull type: V-hull = L×B×0.85, flat bottom = L×B×0.75, round bottom = L×B×0.90. One gallon covers approximately 375 sq ft. Divide wetted area by 375 and multiply by number of coats. Always round up to the nearest gallon.
What type of antifouling paint should I use?
Ablative (self-polishing) paints: best for boats used regularly, release biocide as they wear. Hard paints: better for boats that sit in the water long-term or are trailered frequently. Copper-free paints: required in some areas with copper restrictions. Match paint type to your boating habits.
How often should I apply bottom paint?
Most antifouling paints last one season (6-12 months in the water). Boats in warm, tropical waters may need repainting every 6 months. Trailered boats that are only occasionally in the water may go 2-3 seasons. Inspect the hull annually and repaint when fouling becomes visible.
Can I apply new bottom paint over old paint?
Yes, if the old paint is in good condition and compatible with the new paint. Ablative over ablative is generally fine. Hard paint over ablative is not recommended. If paint is peeling or flaking, remove it completely before repainting. Always check compatibility between paint brands.
What safety precautions should I take when applying bottom paint?
Bottom paint contains biocides (copper, zinc) that are toxic. Always wear: respirator (not just a dust mask), chemical-resistant gloves, eye protection, and old clothes. Work in a well-ventilated area. Dispose of paint waste properly — never wash it into waterways. Check local regulations for paint disposal.