International Envelope Sizes
A Selective Annotated Guide
To ensure economical mailing when materials prepared in one country are to be mailed in a second country, it is necessary to know the envelope sizes commonly used in the second country. Because designers and publishers often do not have ready access to this information, EDS Inc., Editorial & Design Services, has published this selective annotated guide to a variety of commercial, general purpose, and special-use envelopes available in Japan, other countries using the metric system, and North America. ISO (International Organization for Standardization) envelope sizes are the official international metric envelope sizes; however, Japan uses JIS (Japan Industrial Standard) and metricated traditional envelope sizes.
N.B. The Universal Postal Union requires that envelopes for correspondence (1) measure at least 90 mm×140 mm (3 1/2"×5 1/2") and no more than 120 mm×235 mm (4 3/4"×9 1/4"); (2) be oblong, with the dimension of the long side being at least 1.414 times that of the short side; and (3) be made from paper weighing at least 63 gsm (grams per square meter).
In the interest of legibility, Japanese terms are not italicized in the table below.
InternationalEnvelopeSizes.pdf