# Print size calculation evidence

Checked 5 September 2026. The PNG is a generated 1200 × 800 grid, with 200-pixel colored bands on either side. All sample assets and measurement data in this directory are CC0-1.0. They contain no real photo or identity document.

Reproduce: choose pixel-ruler.png at https://jpegconvert.com/print-size-checker, enter the settings in evidence.json, and compare the displayed PPI/crop with the JSON report. Regenerate using Node 22: npm run print-evidence:generate from webapp.

Geometry: convert cm to inches by dividing by 2.54, or mm by 25.4. The physical scale is the smaller print/source ratio for whole-image placement, or the larger ratio for filling the frame. PPI is the reciprocal of that scale. A centered crop uses print width/scale by print height/scale source pixels, capped at the source dimensions. Whole-image placement reports margins on each side. No metadata resolution is read and no pixels are added.

Required whole-frame pixels are rounded upward to ensure each axis meets the target PPI. A tiny floating-point tolerance avoids an extra pixel at exact mathematical integers. This differs from charts that round to the nearest pixel.

These are calculations, not printer measurements. A passing result only establishes the chosen pixel-density threshold; sharpness, color, paper, viewing distance, bleed and printer settings are outside the check.

Sources checked 5 September 2026:
- https://helpx.adobe.com/photoshop/desktop/crop-resize-transform/resize-adjust-resolution/printed-image-resolution.html
- https://helpx.adobe.com/photoshop/desktop/crop-resize-transform/resize-adjust-resolution/resolution-specs-for-printing-images.html