Print DPI / Size Calculator mechanism

Model scope

The forward formula is standard under the stated unit assumptions, but the instrument's claimed reverse resolution and megapixel features are underspecified. The empty honest_label is a concern: the UI should clarify that DPI is pixels per inch/effective image resolution, that centimeter inputs are converted using 2.54 cm per inch, and that print quality depends on more than this arithmetic.

• printSize(in)=pixels/DPI is correct only when pixels is a dimension in pixels and DPI means pixels per inch; width and height must each be divided independently.
• The claimed reverse calculation lacks a stated formula. Required pixel dimensions should be target_width_in×DPI and target_height_in×DPI.
• The claimed required megapixels output lacks a stated formula. It should be (target_width_in×DPI×target_height_in×DPI)/1000000.
• The specification does not define how target sizes in centimeters are converted to inches, how fractional required pixels are rounded, or whether aspect-ratio mismatches are rejected.

Units and conventions

• DPI is interpreted as pixels per inch, numerically equivalent to PPI for this calculation.
• Pixel dimensions are dimensionless pixel counts; print dimensions returned by pixels/DPI are in inches.
• Centimeters are converted using 1 inch=2.54 cm.
• Required megapixels means total required pixels divided by 1000000.
• Target width and height are supplied in the same unit and describe a rectangular print.
• The calculation assumes the image aspect ratio matches the target print aspect ratio unless cropping or distortion is explicitly handled.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "mode": "print_size",
    "pixel_width": 6000,
    "pixel_height": 4000,
    "dpi": 300
  },
  "expected_outputs": {
    "print_width_in": 20,
    "print_height_in": 13.3333333333,
    "print_width_cm": 50.8,
    "print_height_cm": 33.8666666667
  },
  "working": "Width: 6000 ÷ 300 = 20 in. Height: 4000 ÷ 300 = 13.3333333333 in. Width in cm: 20 × 2.54 = 50.8 cm. Height in cm: 13.3333333333 × 2.54 = 33.8666666667 cm."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

A zero-DPI input makes the core division undefined, and the specification provides no stated validation or rejection rule. Unit ambiguity can also produce materially different dimensions if DPI is confused with pixels per centimetre.

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
• BOUNDARY_HAZARD_CATALOG.json