While most of the world uses the ISO 216 A-series (A4, A3, A5), the United States — joined by Canada, Mexico, and the Philippines — follows a completely different paper-size system.
The Origin of Letter Size
The most common US paper size, Letter (8.5 × 11 inches = 216 × 279 mm), has its roots in early American colonial papermaking. Historians trace its dimensions to the Dutch "foolscap" tradition and to the standard size of American writing paper used since the 1700s.
ANSI Paper Sizes
In 1996, the American National Standards Institute (ANSI) formalized a set of paper sizes under ANSI/ASME Y14.1:
- ANSI A — 8.5 × 11 in (Letter)
- ANSI B — 11 × 17 in (Tabloid)
- ANSI C — 17 × 22 in
- ANSI D — 22 × 34 in
- ANSI E — 34 × 44 in
Beyond these, the Architectural series (Arch A through Arch E3) is used for blueprints and engineering drawings.
Letter vs Legal vs Tabloid
- Letter — 8.5 × 11 in — everyday default
- Legal — 8.5 × 14 in — 3 inches longer
- Tabloid — 11 × 17 in — twice the area of Letter
- Ledger — 17 × 11 in — Tabloid rotated 90°
- Junior Legal — 5 × 8 in — notepads and memos
- Half Letter — 5.5 × 8.5 in — organisers
Why the US Didn't Switch
After WWII, ISO 216 was widely adopted in Europe and Asia, but the US, Canada, and a few others kept their traditional sizes. The reasons were practical: too many existing filing cabinets, binders, envelopes, and printer trays were built around Letter.
Practical Consequences
Because Letter and A4 are not the same shape, international documents often need resizing. A4 printed on Letter loses about 3 mm on the sides and gains 18 mm on top and bottom.