Envelope Sizes – DL, C0, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10

Have you ever listen about C Series and DL Business Envelope Sizes? We all write letters to express our thoughts, share with our beloved near and dear ones, and to express gratitude or pain. Since the past messages have been a very efficient way of communication. Businesses officials also have to send various kinds of business documents through the post. Courts also furnish and sanction orders on legalized papers called legal papers and then send it to the person concerned through the post.

Also, various kinds of documents has exchanged amongst two countries and other individuals. But all these tasks share one common thing. The use of the primary material within which we can enclose the letter or document and send it so that it stays confidential until it reaches the target person – an envelope.

Envelopes have been used for centuries to enclose letters and other documents, and they have proved to be useful for the ease of transportation, maintaining of confidentiality, and prevention from threats to security. Envelopes are so helpful that we use them everywhere and for all purpose of sending documents. So, when paper sizes has standardized, it was important that Envelope Sizes too should have standardized. For this, we created the Standard C Series Envelope Sizes. US & North American Envelope Sizes are not covered by ISO 216, that’w why we’ve mentioned them on this page.

ISO 216 Standard for C Envelope Sizes

The dimensions of Paper Sizes in C Series Envelope Sizes have very precisely defined in the ISO 216. All paper and envelope sizes included in the ISO 216 follow a basic rule that they should have an aspect ratio of √2:1. This helps to make these papers easily resizable. The ISO 216 was formed based on the old German DIN 476 Standard which further references a letter by a scientist describing the specialties of the √2:1 aspect ratio. They are as follows:

  • When we fold such a paper or cut precisely into two halves parallel to the two shorter sides, then the two newly created documents also have an aspect ratio of √2:1.
  • When we attach such a paper with another article of the same dimensions along one of the larger sides, the newly formed more prominent paper also has an aspect ratio of √2:1.

These properties help in easy resizing of all the ISO 216 Paper Sizes. The ISO 216 Standard for C Series Envelope Sizes is formed of a few other rules. This also includes standard property.

Rules for C Series Envelope Sizes

  • Every size should have an aspect ratio of √2:1 in the C Series Envelope Sizes (to help with easy resizing). Thus, an A4 Size Paper when folded parallel to its shorter sides easily fits in a C5 Envelope and when wrapped again along the shorter sides will fit comfortably in a C6 Envelope because of the maintaining of aspect ratio √2:1.
  • Any Size C(n) is defined as the geometric mean of the A(n) and B(n) Sizes.

i.e. length of C(n) size = √ (length of A(n) size) × √ (length of B(n) size) and same for the breadth.

This makes the size C(n) an almost exact fit envelope for holding the unfolded sheet of paper of size A(n).

  • As the aspect ratio is an irrational number; the dimensions generally exceed the standard conventions and precision is hard to achieve. For this reason, the sizes are always rounded off to the nearest millimeter.

C Envelope Size Tolerances

ISO has also stated the maximum errors or tolerances that each size can have during production. This is because the output is an error-prone process and mechanical and human errors can always be created.

  1. ± 1.5 mm (0.06 in) for lengths and breadths below 150 mm (5.9 in)
  2. ± 2 mm (0.08 in) for lengths and breadths between 150 mm and 600 mm (5.9 in and 23.6 in)
  3. ± 3 mm (0.12 in) for lengths and breadths above 600 mm (23.6 in)

C Envelope Sizes

The Dimensions of the Envelope Sizes stated in the ISO 216 range from maximum dimensions of 1297 mm × 917 mm (51.5 in × 36.1 in) of the C0 Size to minimum dimensions of 40 mm × 28 mm (1.6 in × 1.1 in) of the C10 Size. The C4 Envelope Size can easily fit unfolded A4 Paper; while the C5 Envelope Size can comfortably fit an A4 Paper folded into half along its shorter sides once; the C6 Envelope Size can comfortably fit an A4 Paper folded into half twice.

C Envelope Sizes Diagram
C Envelope Sizes Diagram

Hence, these C Sizes sometimes referred to as A4 Envelope Size, A5 Envelope Size and A6 Envelope Size. The Sizes of C Series Envelopes can obtain in cm and feet by dividing the millimeter sizes by 10 and the inch sizes by 12 respectively.

C4 Envelope
C4 Envelope
C5 Envelope
C5 Envelope
C6 Envelope
C6 Envelope

Dimensions of C Envelope Sizes

Select the envelope size from the ‘Size‘ field and the unit from the ‘Unit‘ field. This will display the dimensions automatically in the ‘Dimensions‘ box.

229 x 324

Table of Envelope Sizes From C0 to C10

Below is a table for Envelope Sizes from C0 to C10. It contains all the dimensions that you’re looking for.

SizeWidth x Height (mm)Width x Height (in)
C0 Envelope Size917 x 1297 mm36.1 x 51.5 in
C1 Envelope Size648 x 917 mm25.5 x 36.1 in
C2 Envelope Size458 x 648 mm18.0 x 25.5 in
C3 Envelope Size324 x 458 mm12.8 x 18.0 in
C4 Envelope Size229 x 324 mm9.0 x 12.8 in
C5 Envelope Size162 x 229 mm6.4 x 9.0 in
C6 Envelope Size114 x 162 mm4.5 x 6.4 in
C7 Envelope Size81 x 114 mm3.2 x 4.5 in
C8 Envelope Size57 x 81 mm2.2 x 3.2 in
C9 Envelope Size40 x 57 mm1.6 x 2.2 in
C10 Envelope Size28 x 40 mm1.1 x 1.6 in

To find sizes in centimetres, convert mm values to cm by dividing 10 and in feet by dividing inch values by 12. More units here.

DL Envelope Size – Business Envelope Extension

For business envelope we use the DL Business Envelope Size the most. But it doesn’t meet the √2:1 aspect ratio requirements and hence couldn’t include in the C Series Envelope Sizes. But still, we use the DL Business Envelope Size as it can hold most paper sizes and fit them comfortably. Hence, ISO 216 Standards for Envelope Sizes even includes it due to its wide range and worldwide usage.

DL Business Envelope Size
DL Business Envelope Size

The dimensions of the DL Business Envelope Size are 110 mm × 220 mm (4.33 in × 8.67 in). We sometimes consider it small for reliable enveloping, but still, we use it the most.

DL Envelope

The DL Business Envelope Size easily holds an A4 Sheet of Paper when folded parallel to its shorter sides into three equal sections.

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