How accurate is this compared to CAD-measured surface area?

Within 10-15% for conventional hull forms when the correct form coefficient is used. Less accurate for extreme hull shapes like catamarans, trimarans, or heavily stepped hulls.

Which form coefficient should I use for a deep-V hull?

Use 0.82-0.88 for deep-V planing hulls (20+ degrees deadrise). The higher the deadrise angle, the more surface area relative to the projected dimensions.

Does this include the deck and superstructure?

No. This estimates hull shell area only. Add deck area separately (approximately LWL x BWL x 0.85 for typical deck shapes).

Can I use this for multihull surface area?

Calculate each hull separately and sum the results. For catamarans, calculate one hull and multiply by 2. Add bridgedeck area separately.

Marine, Shipbuilding & Boat Manufacturing calculator

Hull Surface Area Estimate Calculator

Estimate the exterior surface area of a boat or vessel hull using basic hull dimensions. Enter waterline length, beam, draft, and a hull form coefficient that accounts for hull shape. The result provides approximate wetted surface area (below waterline) and total hull exterior area for material takeoff, antifouling calculations, fiberglass quantity estimates, and hull weight approximations before detailed CAD models are complete.

What this calculator does

Estimate hull wetted surface area and total exterior surface area using hull length, beam, draft, and a hull form coefficient for material takeoff, coating, and weight calculations.
Use it for early-stage material quantity estimates when detailed CAD surface area is not yet available, particularly for coating, antifouling, and fiberglass material ordering.
The result provides an engineering estimate of hull surface area for material planning before detailed CAD surfaces are available.

Formula used

Wetted surface area = hull form coefficient x LWL x (BWL + 2 x draft)
Total hull exterior area = wetted surface area x 1.35 (adds topsides and transom)

Inputs explained

Waterline length (LWL): Length at the design waterline from the lines plan. For preliminary estimates, use approximately 90-95% of LOA for powerboats.
Beam at waterline (BWL): Maximum beam at the design waterline. Typically 85-95% of maximum beam for planing hulls, 90-100% for displacement hulls.
Design draft: Hull draft at design displacement (canoe body only, exclude appendages). Keel draft for sailboats, hull draft for powerboats.
Hull form coefficient: Accounts for hull shape: flat bottom planing = 0.70, moderate V = 0.78, deep V = 0.85, round bilge displacement = 0.90, sailboat with keel = 0.95.

How to use the result

Use it for early-stage antifouling orders, fiberglass material takeoff, hull weight estimates, and preliminary paint quantity calculations.
This is an approximation based on simplified hull geometry. Actual surface area from CAD models will be more accurate, especially for complex hull forms with chines, spray rails, or tumblehome.

Common questions

How accurate is this compared to CAD-measured surface area? Within 10-15% for conventional hull forms when the correct form coefficient is used. Less accurate for extreme hull shapes like catamarans, trimarans, or heavily stepped hulls.
Which form coefficient should I use for a deep-V hull? Use 0.82-0.88 for deep-V planing hulls (20+ degrees deadrise). The higher the deadrise angle, the more surface area relative to the projected dimensions.
Does this include the deck and superstructure? No. This estimates hull shell area only. Add deck area separately (approximately LWL x BWL x 0.85 for typical deck shapes).
Can I use this for multihull surface area? Calculate each hull separately and sum the results. For catamarans, calculate one hull and multiply by 2. Add bridgedeck area separately.

Last reviewed 2026-05-12.