CALCULATORS / PCB INTERCONNECT AND PACKAGING

Board and enclosure fit calculator

Rectangular board inside rectangular enclosure; edge clearance.

pcb-board-fit.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	lengthMarginmm	widthMarginmm	minimumMarginmm
	6	6	6
	22	6	6

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.

board fits6.00 mm✓ passes

BASELINE INPUTS

boardLength80 mmboardWidth50 mminsideLength90 mminsideWidth60 mmclearance2 mm

CALCULATED

lengthMargin6 mm

widthMargin6 mm

minimumMargin6 mm

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Board and enclosure fit
# Scope: Rectangular board inside rectangular enclosure; edge clearance.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

boardLength = 80 mm
boardWidth = 50 mm
insideLength = 90 mm
insideWidth = 60 mm
clearance = 2 mm

lengthMargin := insideLength-boardLength-2*clearance [mm]
widthMargin := insideWidth-boardWidth-2*clearance [mm]
minimumMargin := min(lengthMargin,widthMargin) [mm]

check board fits: minimumMargin >= 0 mm

scenario alternative: boardLength = 64 mm

Calculated from your source · not saved

Baseline · Baseline

board fits6.00 mm ✓ passes

alternative · alternative

board fits6.00 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.

length margin: lengthMargin = insideLength-boardLength-2*clearance [mm]
width margin: widthMargin = insideWidth-boardWidth-2*clearance [mm]
minimum margin: minimumMargin = min(lengthMargin,widthMargin) [mm]

Original worked example

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

Given

board length: 80 mm
board width: 50 mm
inside length: 90 mm
inside width: 60 mm
clearance: 2 mm

Calculated

length margin: 6 mm
width margin: 6 mm
minimum margin: 6 mm

Assumptions and limits

Rectangular board inside rectangular enclosure; edge clearance.

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: Board and enclosure fit. Inputs: board outline; keepouts; hole and connector locations; tolerances. Outputs: clearances; alignment errors. Model scope: Explicit stackup and trace/via geometry; empirical models identified. 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: board outline, keepouts, hole and connector locations, tolerances
Outputs: clearances, alignment errors
Modes: calculate, compare, sweep
Drawing: Layer viewer and cross section

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