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International Envelope Series



Belonging to the ISO 216 standard, E9 is a unique paper size that holds its own significance. This particular size, measuring 64 x 91 mm, is part of the E series in the ISO standards. The E series is specifically designed for envelopes and is often overlooked due to its specialized nature.

The dimensions of E9 are meticulously calculated using a ratio based on the square root of two (√2). This aspect ratio ensures that when you cut or fold an E9 sheet in half across its larger dimension, you get two smaller sheets with the same aspect ratio. It's this ingenious design principle that makes all ISO paper sizes harmoniously compatible.

E9 paper dimensions


View All International Envelope Series

2A046.81 x 66.221189 x 1682119 x 1683370 x 4768
A120.51 x 0.7113 x 181 x 237 x 51
4A066.22 x 93.621682 x 2378168 x 2384768 x 6741
A110.71 x 1.0218 x 262 x 351 x 74
A101.02 x 1.4626 x 373 x 474 x 105
A3+12.95 x 19.02329 x 48333 x 48933 x 1369
A1+23.98 x 35.98609 x 91461 x 911726 x 2591
A0+35.98 x 50.87914 x 129291 x 1292591 x 3662
A64.13 x 5.83105 x 14811 x 15298 x 420
A55.83 x 8.27148 x 21015 x 21420 x 595
A48.27 x 11.69210 x 29721 x 30595 x 842
A311.69 x 16.54297 x 42030 x 42842 x 1191
A91.46 x 2.0537 x 524 x 5105 x 147
A216.54 x 23.39420 x 59442 x 591191 x 1684
A82.05 x 2.9152 x 745 x 7147 x 210
A123.39 x 33.11594 x 84159 x 841684 x 2384
A72.91 x 4.1374 x 1057 x 11210 x 298
A033.11 x 46.81841 x 118984 x 1192384 x 3370

While it may not be as commonly recognized as A4 or B5 sizes from other ISO series, E9 has a crucial role in specific applications. Its dimensions make it an ideal choice for enclosing A8 documents without any need for folding or creasing them. This makes it highly efficient and practical for businesses dealing with A8-sized documents such as tickets or small leaflets.

Interestingly enough, despite being part of an international standard, the usage of E9 varies significantly across different regions worldwide. While some countries have fully adopted ISO standards including the E series, others continue to use local standards like ANSI in America.

While it might seem like just another paper size at first glance, delving deeper into its design principles and practical applications reveals how integral E9 is within certain niches. Its existence underlines how comprehensive and well-thought-out international paper size standards truly are.

Other Formats in the International Envelope Series

Interesting facts about E9

1. E9 paper size is not a standard paper size

E9 paper size does not belong to the ISO 216 standard series of paper sizes. It is a non-standard size that falls outside the commonly used A, B, and C series.

2. E9 paper dimensions are not fixed

Unlike other standard paper sizes, E9 does not have fixed dimensions. The exact measurements of an E9 sheet can vary depending on the specific requirements or preferences of the user or organization.

3. E9 is often used for large-scale engineering drawings

E9 paper is commonly used in engineering and architectural fields for creating large-scale technical drawings, blueprints, or plans. Its larger size allows for detailed representations of complex structures or designs.

4. E9 can be customized to fit specific needs

Since there are no standardized dimensions for E9 paper, it can be easily customized to fit specific requirements. This flexibility makes it suitable for unique projects that demand unconventional sizes.

5. The origin of the "E" designation remains unclear

The exact origin and meaning behind the "E" designation in E9 remain uncertain. Unlike other series like A, B, and C which have historical explanations (e.g., A stands for "arithmetic"), there is no widely accepted explanation for the letter "E" in this context.

6. Limited availability of pre-cut E9 sheets

Due to its non-standard nature, finding pre-cut sheets of E9 paper might be challenging compared to more common sizes like A3 or A2. However, it can still be obtained by custom cutting larger sheets or through specialized printing services.

7. E9 paper can be used for artistic purposes

Artists and designers sometimes choose E9 paper for large-scale artworks or installations. Its size provides ample space to create visually impactful pieces that command attention.

8. E9 is not widely recognized outside certain industries

While E9 is well-known within engineering, architectural, and design circles, it may not be familiar to individuals outside these industries or those who do not frequently encounter large-format prints or drawings.

9. The aspect ratio of E9 paper is not fixed

The aspect ratio (width-to-height ratio) of an E9 sheet can vary depending on the specific dimensions chosen by the user. This allows for further customization based on the intended use or visual preferences.

10. Some countries have their own non-standard series

In addition to the ISO 216 standard series, some countries have their own non-standard series of paper sizes, including unique sizes similar to E9. These variations reflect regional preferences and specific industry requirements.