No universal pixels-per-inch assumption
Convert pixels to inches at a stated PPI
Pixels become a physical length only after you state the print density. The calculator keeps that assumption visible.
Formula, PPI, and examples
How to convert pixels to inches
Inches = pixels ÷ PPI.
At 300 PPI, 1200 px ÷ 300 = 4 in. A 3000 × 2000 px image is 10 × 6.666667 in.
Pixel count alone does not define a physical length. At 96 PPI, 1200 px is 12.5 in; at 300 PPI, the same 1200 px is 4 in.
For CSS layout only, the reference-unit rule is 96 CSS px = 1 CSS in. That convention does not report actual device pixels or set an image's print size.
Private browser calculation