Letter – US Paper Sizes

216 × 279mm | 8.5 × 11in

North America, including the US, Canada and parts of Mexico, is the only area of the first world that doesn’t use the ISO 216 standard paper sizes, instead they use Letter, Legal, Executive and Ledger/Tabloid paper sizes and those that have been formalised in ASME Y14.1M – Metric Drawing Sheet Size & Format. US Envelope Sizes are also non ISO 216.

ANSI (American National Standards Institute) defined a regular series of paper sizes based around the Letter (8.5″ x 11″) format, with this becoming the A sizes and larger sizes being B,C,D & E. Surprisingly these ANSI standard sizes were defined in 1995 well after the ISO standard sizes. ANSI A sized paper is commonly referred to as Letter and ANSI B as Ledger or Tabloid.

Unlike the ISO standard sizes which have the single aspect ratio of 1:root2, ANSI standard sizes have two aspect ratios 1:1.2941 and 1:1.5455 which means that enlarging and reducing between the sizes is not as easy as with the ISO sizes and leaves wider margins on the enlarged/reduced document.

Other paper size standards issued by ANSI include:

  • ANSI INCITS 151-1987 – Bond Papers and Index Bristols – Common Sheet Sizes
  • ANSI INCITS 96-1983 – Forms, Paper Sizes for Single-Part Continuous Business

B Plus, or Super B as it is sometimes known, has dimensions of 13″ x 19″ (329mm x 483mm). This size is the ANSI B size with a 1″ margin for print bleed all the way round. It is sometimes known as A3+ or Super A3 in countries that use ISO 216 paper sizes. European manufacturers sometimes give this size as 330mm x 482mm.

North America also has a special series of paper sizes defined for architectural purposes, in general these have aspect ratios of 4:3 or 3:2. These aspect ratios are very similar to the aspect ratio used for computer screens.