Paper Sizes
A-series, US and B-series paper dimensions in millimeters, inches — and pixels at whatever DPI you're designing for.
Frequently asked questions
Why is A4 210 × 297 mm and not something round?
The A series keeps a √2 aspect ratio, so each size is exactly half the previous one: cut A3 in half, get two A4s — and anything laid out for one scales perfectly to another. A0 is defined as 1 m² of area; A4 is four halvings later.
Which DPI should I use?
300 DPI is the print standard (crisp text and photos); 150 works for large posters viewed from a distance; 72–96 matches on-screen documents. A4 at 300 DPI is 2480 × 3508 px — the number every scanned-document spec asks for.
A4 or US Letter — what breaks between them?
Letter (8.5 × 11 in) is wider and shorter than A4. A Letter-designed PDF printed on A4 clips the sides or shrinks; the fix is "scale to fit" when printing, or designing inside the overlap (about 210 × 279 mm) when a document must print on both.
Last updated: 2026-07-13