DIN long

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Window envelope in DL format

DIN long is the colloquial term for several similar formats for envelopes that were originally intended to be used for DIN A4 letterheads that were folded horizontally twice, as well as for other insert formats suitable for these envelopes. The designation is based on the paper formats according to DIN .

The following are standardized according to DIN:

  • the envelope sizes
    • DL : 110 mm × 220 mm
    • C6 / C5: 114 mm × 229 mm
  • the paper size (final size) 1/3 A4: 99 mm × 210 mm
  • the paper format (final format) by folding A4 letterhead for DL ​​or C6 / C5 window envelopes: 105 mm × 210 mm

Distribution in Germany and Austria

In Germany and Austria, envelopes in DL and C6 / C5 format are the most widely used envelopes in business correspondence . The standardized design with a viewing window allows documents designed according to DIN 5008 and folded to 105 mm × 210 mm to be sent without additional address and sender lettering on the envelope. The window is 90 mm wide and 45 mm high, 20 mm from the left and 15 mm from the lower edge.

Many print products, such as leaflets, short messages and inserts in booklet form, are specially designed for sending in DIN long envelopes, as this envelope format, in addition to the C6 format, which is not very suitable for this purpose, causes the lowest postage costs.


This envelope is rarely used in Switzerland. Whereas in the past only C6 was used, today C5 is standard. For Swiss Post, the costs of sending a C5 are only marginally higher than those of a DIN long envelope and are therefore just as expensive for customers in Switzerland. On the other hand, the advantages of the single folding of the C5 outweigh the double folding of the DIN long.


  1. a b DIN 678-1 envelopes - Part 1: Formats
  2. DIN EN ISO 216 writing paper and certain groups of printed matter - final formats - A and B rows and marking of the machine direction
  3. DIN 680 window envelope - formats and window position
  4. DIN 5008 writing and design rules for word processing