PPI
PPI, or pixels per inch, expresses pixel density relative to a physical inch.
PPI is used when relating raster pixels to physical output size. The pixel dimensions of the image remain important for determining available detail.
Pixels mapped to a physical inch
PPI is used when relating raster pixels to physical output size. The pixel dimensions of the image remain important for determining available detail. In practical terms, PPI belongs to the visual-production layer. Knowing that layer is important because it tells you what the term can change, what it cannot change, and where to look when something behaves unexpectedly.
Calculating 3000 pixels across a 10-inch print
A 3000-pixel-wide image printed at 10 inches is effectively 300 pixels per inch.
Where PPI connects digital images to print size
You do not need to memorize the term in isolation. It becomes useful when you can recognize it in the tool, browser, file or conversation where the concept is doing real work.
PPI is not printer DPI
PPI, or pixels per inch, expresses pixel density relative to a physical inch. By contrast, DPI, or dots per inch, describes the density of printed dots produced by an output device. The two can appear in the same project, but they describe different parts of the work and should not be used as interchangeable labels.
The mistake: treating metadata as extra resolution
The common mistake is to use PPI as if it also meant DPI. That blurs two separate decisions and usually sends troubleshooting in the wrong direction. A better test is practical: Calculate PPI from pixel dimensions and physical output size rather than changing metadata and expecting new image detail.
Why pixel dimensions and physical size must agree
In day-to-day work, PPI matters when pixel density needs to be described. The practical value is not the vocabulary itself; it is being able to identify the right control, file, setting or decision when the concept becomes relevant.
A 3000-pixel-wide image printed at 10 inches is effectively 300 pixels per inch. That example is useful because it turns the definition into something you can recognize, test and discuss with other people working on the same project.
Related terms worth learning next
Sources and further reading
Use these references when you need documentation-level detail, specifications or product-specific behavior beyond the plain-English explanation above.