PPI is pixels per inch on paper. In planning, people often use it interchangeably with DPI: pixels ÷ print inches.
How print size is calculated
Print width (inches) = pixels ÷ DPI. Centimeters = inches × 2.54. For example, a :pixels px image at 300 DPI prints at about :size_300_cm.
What DPI should you use?
300 DPI is the usual target for photo-quality prints viewed up close. 150–200 DPI often works for posters. Large-format and outdoor prints can go much lower because viewing distance is greater.
Pixels vs. DPI metadata
Changing the DPI tag in software does not add detail. Only the pixel count and the physical print size determine effective resolution. Use a calculator with real pixel dimensions.
FAQ
How big can I print my photo?
Divide each pixel dimension by your target DPI. At 300 DPI, :pixels px prints about :size_300_cm. At 150 DPI the same file prints about :size_150_cm.
Is PPI the same as DPI for printing?
For planning print size, people often use DPI and PPI interchangeably to mean pixels per inch. Printers still use dots of ink; your planning number is pixels ÷ print inches.