CALCULATORS / MARINE AND UNDERWATER DEVICES

Vessel displacement and draft calculator

Fresh or salt water hydrostatic displacement at supplied density.

marine-displacement.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	displacementL
	97.561
	78.0488

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

displacement volume budget97.56 L✓ passes

BASELINE INPUTS

mass100 kgdensity1025 kg/m^3

CALCULATED

displacement97.561 L

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Vessel displacement and draft
# Scope: Fresh or salt water hydrostatic displacement at supplied density.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

mass = 100 kg
density = 1025 kg/m^3

displacement := mass/density [L]

check displacement volume budget: displacement <= 120 L

scenario alternative: mass = 80 kg

Calculated from your source · not saved

Baseline · Baseline

displacement volume budget97.56 L ✓ passes

alternative · alternative

displacement volume budget78.05 L ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

displacement: displacement = mass/density [L]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

mass: 100 kg
density: 1025 kg/m^3

Calculated

displacement: 97.561 L

Assumptions and limits

Fresh or salt water hydrostatic displacement at supplied density.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Vessel displacement and draft. Inputs: hull submerged geometry; water density; payload. Outputs: buoyancy; draft estimate. Model scope: Hydrostatics and calibrated hydrodynamic coefficients. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: hull submerged geometry, water density, payload
Outputs: buoyancy, draft estimate
Modes: calculate, compare, sweep
Drawing: Hull and underwater load diagram

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS