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US Paper Sizes
US Paper Sizes
North America — including the United States, Canada, and parts of Mexico — is one of the few regions in the world that does not use the ISO 216 standard. Instead, it relies on a distinct set of paper sizes rooted in historical convention, the most prevalent being Letter, Legal, and Ledger/Tabloid. The everyday sizes were later complemented by a formal technical series defined by the American National Standards Institute (ANSI) and codified in ASME Y14.1.
Main Characteristic
Unlike the ISO 216 A series, US paper sizes do not share a single consistent aspect ratio. Each size has its own proportions, which means that scaling content from one size to another — say, from Letter to Legal — will alter the layout and require manual adjustment of margins and design elements. This stands in contrast to the ISO system, where halving or doubling a sheet always yields another standard size with identical proportions.
Measurement System
Everyday sizes: The core US sizes — Half Letter, Letter, Legal, and Ledger/Tabloid — emerged from historical trade practice and were never derived from a single mathematical formula. Letter (8.5 × 11 in) became the de facto standard for general office and personal use.
ANSI series: In 1996, ANSI formally adopted the ASME Y14.1 standard, which defined a series of sizes for technical and engineering drawings. ANSI A corresponds to Letter (8.5 × 11 in), with each subsequent size (B, C, D, E) doubling the area of the previous one — similar in logic to the ISO system. Cutting an ANSI B (Ledger/Tabloid) sheet in half yields two ANSI A (Letter) sheets.
Common usage: Letter is the dominant size for everyday printing, business correspondence, and personal documents. Legal is used in legal and governmental contexts. Ledger/Tabloid serves printing, publishing, and spreadsheet work requiring more horizontal space.