Convert physical pixel density
Pixel density describes a count of image or display pixels per physical length. CalcOS converts supported values through pixels per meter. Pixel pitch is the reciprocal physical length occupied by one pixel.
This converter does not calculate density from pixel dimensions and screen size; the PPI Calculator performs that separate task.
PPI, printer DPI, and CSS resolution are different contexts
| Term | Meaning | Converter treatment |
|---|---|---|
| PPI | Image or display pixels per physical inch | Supported as px/in |
| Printer DPI | Output-device dots per physical inch | Not converted as pixels |
| CSS dppx | Device pixels per CSS reference pixel | Separate W3C resolution context |
| Pixel pitch | Physical length per pixel | Supported reciprocally |
A CSS pixel is not necessarily a device pixel
CSS defines reference relationships for layout units, including 96 CSS px per CSS inch, while browsers map those units to displays according to viewing conditions and device behavior. That reference relationship does not certify the physical density of a screen.
Metadata does not resample an image
Changing or converting a PPI metadata value does not add or remove pixels. Physical output size is pixel count divided by the chosen output density, and software or printer settings may override metadata.
Why zero is rejected
Zero pixel density has no finite reciprocal pixel pitch. Since pixel density describes a physical scale, CalcOS requires a finite value greater than zero.
Authoritative references: BIPM definition of the metre, W3C CSS Values and Units Level 4, and NIST glossary.