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CALCULATORS / ASSEMBLY, CAPACITY AND MANUFACTURING ECONOMICS

Make-or-buy cost comparison calculator

Linear fixed/variable cost comparison; account units, capacity effects omitted.

manufacturing-make-or-buy.napkin / editable
✓ checks pass

SCENARIO COMPARISON

Compare the numbers.

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

ScenariomakeCostbuyCostsavings
10000120002000
90009600600

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.

make cheaper example2000.00 ✓ passes

BASELINE INPUTS

CALCULATED

makeCost10000
buyCost12000
savings2000

Edits change the baseline source.

Calculated from your source · not saved
Baseline · Baseline
make cheaper example2000.00 ✓ passes
alternative · alternative
make cheaper example600.00 ✓ 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.

make cost
makeCost = fixed+quantity*makeUnit
buy cost
buyCost = quantity*buyUnit
savings
savings = buyCost-makeCost

Original worked example

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

Given

quantity
1000
fixed
5000
make unit
5
buy unit
12

Calculated

make cost
10000
buy cost
12000
savings
2000

Assumptions and limits

Linear fixed/variable cost comparison; account units, capacity effects omitted.

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: Make-or-buy cost comparison. Inputs: tooling; labor; equipment; supplier prices; quantity. Outputs: cost curves; break-even demand. Model scope: Explicit process times, yield and costs supplied by the user. 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: tooling, labor, equipment, supplier prices, quantity
  • Outputs: cost curves, break-even demand
  • Modes: calculate, compare, sweep
  • Drawing: Process graph and cost curves

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

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