Margin vs Markup Converter implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t4-259

Effect

Computation or source lookup only

Input and validation requirements

A zero cost makes markup undefined, and an unlabelled margin value such as 50 is ambiguous between 50% and decimal 50. The converter should reject zero denominators and enforce explicit percentage units.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "cost": 80,
    "price": 100,
    "currency": "USD",
    "basis": "per item"
  },
  "expected_outputs": {
    "margin_percent": 20,
    "markup_percent": 25
  },
  "working": "margin=(price-cost)/price=(100-80)/100=20/100=0.20=20%. markup=(price-cost)/cost=(100-80)/80=20/80=0.25=25%."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json