OffsetCalc

Naval architecture tool for hull lines plans and offset tables. Enter your offsets, visualise the hull form, and calculate hydrostatics — all in the browser.

Enter Offset Table View Lines Plan Learn the Basics

Offset Table Editor

Enter half-breadths at stations × waterlines. Import/export CSV. Built-in sample vessels to get started immediately.

Lines Plan

Interactive SVG lines plan — Body Plan, Sheer Plan, and Half-Breadth Plan. Export to PDF for documentation.

3D Hull View

Three.js wireframe hull rendered from your offset data. Rotate, zoom and inspect the hull form from any angle.

Hydrostatics

Simpson's Rule integration: displaced volume, LCB, LCF, Cb, Cw, Cm, Cp, KB, BM, KM. Bonjean curve chart.

What is an Offset Table?

An offset table is the numerical representation of a ship's hull form. It lists the half-breadth distances from the centreline to the hull surface at each station (cross-section) and waterline (horizontal plane).

From these numbers you can reconstruct the complete three-dimensional hull form — the body plan, sheer plan, and half-breadth plan — and calculate all hydrostatic properties.

Sample Offset Table (half-breadths in metres)

Stn	WL0	WL0.5	WL1.0	WL1.5	WL2.0
0 (AP)	0.40	1.20	1.80	2.20	2.50
5 (Mid)	2.10	3.35	3.58	3.60	3.60
10 (FP)	0.05	0.35	0.70	1.05	1.35

Sample Vessels

Ready to use

Patrol Craft 40Realistic hull

40m × 7.2m × 2.0m draft

Cb ≈ 0.55

Load this vessel

Box Barge 30Learning example

30m × 8.0m × 1.5m draft

Cb ≈ 0.95

Load this vessel

Simpson's Rule integration

CSV import & export

PDF lines plan export

Body / Sheer / Half-breadth plans

Three.js 3D wireframe

Mobile responsive