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Measuring Paper

ISO and North American Sheet Sizes

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compare letter size to A4 size paper

Side-by-side comparison of letter size to A4 size paper.

Do you know the difference between "Letter" size paper (8.5 x 11 inches) and A4 paper? Letter and A4 sizes are comparable in use. Depending on where you are, each size is the standard for letters, magazines, copy machines, and desktop printing. Comparing them graphically (sidebar image) is the easiest way to see the difference.

A4 (210 mm x 297 mm), the standard in most countries outside North America, is not quite as wide as Letter size (approx. 216 mm x 279 mm) paper and is longer. When exchanging documents this difference can cause problems. For example, a document formatted for A4 paper must be reformatted (possibly causing page numbering and referencing errors) to print on Letter size -- otherwise information at the bottom of the longer A4 page may be lost.

    TIP: When photocopying A4 pages to Letter size paper, reduce the pages 94% to fit the shorter paper. When photocopying Letter size pages to A4 paper reduce the pages 97% to fit the slightly narrower page (or risk losing margins or text that appears near the page edges).

For a better understanding of common paper sizes used by other countries, EDS, Inc. provides a Guide to International Paper Sizes [offsite link] with a comprehensive set of tables, comparisons, and conversion tips.

To get a quick overview, see these definitions:
ISO Sheet Sizes | North American Sheet Sizes

Beyond the Desktop
While desktop printers typically use letter size papers, for commercial printing there is a whole other world of paper measurements to consider. A few of specific interest to desktop publishing:

  • Parent Sheets - the larger sheets of paper used by commercial printers that are typically cut or folded into smaller sizes

  • Cut Sizes - the smaller sheets of paper used by quick printers and desktop printers including letter and tabloid sizes

  • Basis Weight - the weight, in pounds, of 500 sheets of any particular standard size of paper

  • Basic Size - the customary standard sheet size that is used to determine the basis weight for 500 sheets (ream) of paper

The purpose of this article is simply to acquaint you with some of the terminology associated with measuring paper. Other tutorials will address more detailed use of this information.

Next > Measuring Resolution: SPI, PPI, DPI, LPI

Intermediate Tasks > Measurements Systems > Measuring Paper

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