North American paper follows its own set of standards built around the 8.5 × 11 inch Letter sheet. This reference covers the common office sizes — Letter, Legal, Tabloid and more — plus the full ANSI A–E engineering series, in inches, millimetres, and centimetres.
How it works
US sizes are defined in inches, so the metric figures are conversions using 1 inch = 25.4 mm. Unlike the ISO A series, US paper has no single aspect ratio. Instead the ANSI series alternates between two shapes as you fold up: ANSI A (Letter) and ANSI C share one ratio, while ANSI B (Tabloid), D, and E share another. That is why a Letter sheet scaled to Tabloid does not fill the page the way A4 scales cleanly to A3.
The neat exception is Tabloid/Ledger = 11 × 17 in, which is exactly two Letter sheets side by side — the same size as ANSI B. That makes Letter and Tabloid the one pair in the US system that tiles as cleanly as the ISO series.
Example and notes
To print a Tabloid spreadsheet onto two Letter pages, split it down the middle — each half is exactly Letter size. To enlarge a Letter drawing to ANSI C (17 × 22 in), scale by 200% in area, doubling both dimensions, because ANSI C is four Letter sheets in a 2 × 2 arrangement.
Letter (8.5 × 11 in / 216 × 279 mm) is close to but not the same as A4 (210 × 297 mm): Letter is wider and shorter. When sharing documents internationally, set the page size explicitly so margins and page breaks survive the switch between standards.