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International Envelope Series



Belonging to the ISO 216 series, the C5 paper size is a versatile and widely used format. It measures 162 x 229 millimeters or approximately 6.4 x 9 inches, making it an ideal choice for various professional and personal applications.

The C5 size is part of the 'C' series in the ISO standard, designed specifically to accommodate envelopes. This particular size is perfectly suited to hold A5 sheets or A4 sheets folded in half, providing a practical solution for mailing documents without creasing them.

C5 paper dimensions


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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

Interestingly, the dimensions of C5 are derived from an aspect ratio of √2:1 like all sizes in the ISO 216 series. This unique feature ensures that when two same-sized pieces are placed side by side or one sheet is halved parallel to its shorter sides, it results in two smaller sheets with exactly the same aspect ratio.

In comparison with ANSI standards prevalent in North America, C5 closely aligns with Half Letter size but offers slightly more room due to its larger dimensions. This makes it a preferred choice for businesses seeking a universal paper format that can cater to both European and American markets.

From brochures and flyers to direct mail campaigns and corporate correspondence - C5's adaptability across multiple uses underscores its importance in today's print industry. Its compatibility with most printers further enhances its appeal among users worldwide.

In conclusion, whether you're aiming for professional presentation or efficient packaging, leveraging the benefits of C5 paper size can significantly elevate your communication strategy.

Other Formats in the International Envelope Series

Interesting facts about C5

1: C5 Paper Size

C5 paper is part of the ISO 216 standard series, which defines the sizes of paper used globally. It measures 162 mm × 229 mm or approximately 6.4 inches × 9 inches.

2: Envelope Compatibility

C5 paper is commonly used for envelopes that fit A5-sized documents folded once. This makes it ideal for mailing letters, invitations, and greeting cards.

3: Half of A4

The C5 size is exactly half the size of an A4 sheet. When an A4 sheet is folded in half, it becomes a C5 size.

4: International Correspondence

C5 envelopes are widely used for international correspondence as they can accommodate unfolded A5 sheets without any folding required.

5: Business Stationery

C5 paper is often used for business stationery such as letterheads and invoices due to its convenient size and professional appearance.

6: Common Invitation Size

In many countries, C5 envelopes are a popular choice for wedding invitations and other formal event invitations due to their elegant proportions.

7: European Standardization

The ISO standard series was first introduced in Europe in the mid-20th century to promote uniformity in paper sizes across different countries and industries.

8: Historical Origins

The ISO standard series was based on the German DIN standard introduced in the early 20th century, which aimed to simplify paper sizes and reduce waste during printing processes.


It's important to note that while C5 paper is a specific size, the term "C5" can also refer to an envelope size that fits C5 paper. The ISO 216 standard defines both paper sizes and corresponding envelope sizes.