Wetted Surface Area (WSA)

Estimate S (submerged hull area) via Holtrop–Mennen or a simplified displacement method.

Method

Choose empirical model.

LWL — Length on Waterline (m)

Enter a positive number.

BWL — Beam on Waterline (m)

Enter a positive number.

T — Draft (m)

Enter a positive number.

C_B — Block Coefficient

Enter a value between 0 and 1.

C_M — Midship Coefficient

Enter a value between 0 and 1.

C_WP — Waterplane Coefficient

Enter a value between 0 and 1.

∇ — Displacement Volume (m³)

Only used by the simplified method.

Speed (kn) — optional (for C_f)

If provided, ITTC ’57 friction coefficient is shown.

Result

— m²

— ft²

Enter inputs, select method, and click Calculate.

Report: Wetted Surface Area (WSA)

Method — —

—

How it works (formulas)

Holtrop–Mennen (empirical):

\( S = L_{WL}\,(2T + B_{WL})\,\sqrt{C_M}\,\left[0.453 + 0.4425\,C_B - 0.2862\,C_M - 0.003467\,(B_{WL}/T) + 0.3696\,C_{WP}\right] \)

Simplified (displacement-based):

\( S \approx 1.7 \times \nabla^{2/3} \), where \( \nabla \) is displacement volume (m³).

Friction coefficient (optional):

ITTC ’57: \( C_f = \frac{0.075}{(\log_{10}Re - 2)^2} \), with \( Re = \frac{V\,L_{WL}}{\nu} \), \( V \) in m/s, \( \nu \approx 1.19\times10^{-6}\,m^2/s \) (seawater, ~15 °C).