Pixels and physical size
Physical inches equal pixels divided by pixels per inch. Required pixels equal physical inches multiplied by pixels per inch. Metric measurements are converted using exactly 2.54 centimetres or 25.4 millimetres per inch.
PPI and DPI terminology
PPI describes image pixels per physical inch. DPI technically describes printer dots per inch. Because many users and print specifications use “DPI” for image sizing, the interface acknowledges both terms while the underlying image calculation uses pixels per inch.
Effective print resolution
Effective resolution is calculated independently for width and height. ReadyForPrint reports the lower axis because that is the limiting value. A metadata DPI tag does not add image detail.
Quality descriptions
The quality labels are planning guidance, not guarantees. Viewing distance, printer, paper, image content, sharpening and production method all affect perceived output. We use 300 PPI as a common close-viewed target, not a universal requirement.
Bleed and safe margins
Bleed is added to every outer edge. A 3 mm bleed increases both width and height by 6 mm. Safe margin is subtracted from every inner edge. Printer and publisher specifications always take precedence.