DPI
A resolution unit measuring dots per inch. Primary metric for print quality; irrelevant for web display.
DPI (Dots Per Inch) measures dots within one inch (2.54 cm), indicating resolution in printing and scanning. Higher DPI means denser dots and finer output quality.
Common DPI benchmarks:
- 72 DPI: Legacy Mac display reference. Adequate for screens, too coarse for print
- 150 DPI: Newspapers and large posters viewed from distance
- 300 DPI: Commonly taken as the target for commercial printing of books, magazines, and photo prints
- 600-1200 DPI: High-quality art prints and precise line art
PPI (Pixels Per Inch) is often confused with DPI. PPI refers to display pixel density; DPI to physical print dot density. Though technically distinct, editors often treat them interchangeably. Retina display density varies by model; models around 218-264 PPI sit at roughly twice the density of standard displays (96-110 PPI).
For web images, DPI metadata has no effect on HTML display size (behaviour of major browsers as of 2026). Browsers render by pixel dimensions only - a 1000x800 image displays identically at 72 or 300 DPI. DPI matters only for printing: print size (inches) = pixels / DPI. Rewriting just the DPI value in an editor therefore adds no pixels, so detail at the same print size is unchanged; when print is the goal, decide the pixel count from the required print size and DPI first.