PPI and DPI are related, not interchangeable
Learn why image pixels use PPI, printer dots use DPI, and PaperSize calculates a raster canvas from physical inches and PPI.
Read articlePaper and pixel essentials
Understand every dimension in the result
Three practical articles separate PPI from printer DPI, explain the ISO A series, and turn a physical format into an image canvas without hidden assumptions.
How the ISO A-series paper sizes fit together
See the exact millimetre bases for A3, A4, and A5, why the family keeps a common proportion, and why Letter and Legal are separate.
Read articleA4 vs US Letter: 210 × 297 mm vs 215.9 × 279.4 mm
A4 is 210 × 297 mm; US Letter is 215.9 × 279.4 mm. Letter is 5.9 mm wider and 17.6 mm shorter, so layouts and pixel canvases differ.
Read article