CALCULATORS / GEOMETRY AND MASS PROPERTIES

Hollow rectangular enclosure volume calculator

Rectangular hollow enclosure with uniform walls and closed ends.

geometry-volume.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	outercm^3	cavitycm^3	materialcm^3
	1600	1349.46	250.536
	1280	1071.22	208.776

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.

positive cavity6.00 mm✓ passes

BASELINE INPUTS

length200 mmwidth100 mmheight80 mmwall3 mm

CALCULATED

outer1600 cm^3

cavity1349.5 cm^3

material250.54 cm^3

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Volume of engineering solids
# Scope: Rectangular hollow enclosure with uniform walls and closed ends.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

length = 200 mm
width = 100 mm
height = 80 mm
wall = 3 mm

outer := length*width*height [cm^3]
cavity := (length-2*wall)*(width-2*wall)*(height-2*wall) [cm^3]
material := outer-cavity [cm^3]

check positive cavity: 2*wall < height

scenario alternative: length = 160 mm

Calculated from your source · not saved

Baseline · Baseline

positive cavity6.00 mm ✓ passes

alternative · alternative

positive cavity6.00 mm ✓ 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.

outer: outer = length*width*height [cm^3]
cavity: cavity = (length-2*wall)*(width-2*wall)*(height-2*wall) [cm^3]
material: material = outer-cavity [cm^3]

Original worked example

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

Given

length: 200 mm
width: 100 mm
height: 80 mm
wall: 3 mm

Calculated

outer: 1600 cm^3
cavity: 1349.46 cm^3
material: 250.536 cm^3

Assumptions and limits

Rectangular hollow enclosure with uniform walls and closed ends.

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: Volume of engineering solids. Inputs: solid type; dimensions; cavities. Outputs: volume; displaced volume. Model scope: Ideal solids and explicitly described coordinate frames. 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: solid type, dimensions, cavities
Outputs: volume, displaced volume
Modes: calculate, compare, sweep
Drawing: Parametric solid

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