The different types of envelope

The envelope is the best shipping material to send letters by post. There are many types of envelopes to ship a wide range of objects: an invitation or a bill, a small fragile object, a book or a catalogue, etc. And there are also many sizes. How to choose the right size of envelop?


  1. The different sizes of envelopes: what are the dimensions of each size?
  2. The different types of envelope
  3. How to choose the right envelope?


padded envelopes

1. The different sizes of envelopes: what are the dimensions of each size?

The different sizes of the standard letter

The dimensions of the envelope are related to the size of paper you want to send. The international standard ISO 216 describe the different sizes of paper with the letter A followed by a figure (A3, A4, A5, etc.). And the international standard ISO 269 describes the different sizes of envelopes with the letter C followed by a figure (C3, C4, C5, etc.). The two standards were designed to match each other.

For example, if you want to send an A4 paper without folding it, you can use a C4 envelope. If you want to fold the paper, you can use the C5, C6, C5/6 or DL envelope (according to the number of folds you want to make).

Here is a table with the standard sizes of letter with their equivalence in paper size:

Size of envelopeDimensions of the envelope (H x L)Equivalence in paper size
C332.4 x 45.8 cmA3
C422.9 x 32.4 cmA4 (A3 folded in half)
C516.2 x 22.9 cmA5 (A4 folded in half)
C5/611.4 x 22.9 cmA4 folded in three / A5 folded in half
C611.4 x 16.2 cmA4 folded in four (postcard size)
C78.1 x 11.3 cmA5 folded in four
DL11 x 22 cmA4 folded in three / A5 folded in half

The DL envelope, a specific size

The DL envelope was created in the 1920's, nowadays it became inescapable to send business mails and more generally professional letters. This type of envelope comes from Germany and doesn't belong to the C-size of envelopes but it quickly took a rightful place in the international standard ISO 269. Yet, a larger size, the C5/6 (11.4 x 22.9 cm), is going to supplant the DL size.

padded envelope
Bubble envelopes

The other sizes of envelopes

But, there are several other sizes of envelope. For example, the B size of envelopes. The logic is the same: each size has a letter followed by a figure (B4, B5, etc.). It's the intermediate size between the A size and the C size. In terms of dimensions, it is between An and An-1. For example, the B4 size (25 x 35.3 cm) is between the A4 size (21 x 29.7 cm) and the A3 size (29.7 x 42 cm). A B4 envelope can contain a C4 envelope.

There are also other sizes of envelopes: E4, E5 and DA.

Here is a board with the other sizes of envelopes:

Size of envelopeDimensions of the envelope (H x L)
B425 x 35.3 cm
B517.6 x 25 cm
E428 x 40 cm
E520 x 28 cm
DA11.5 x 22.5 cm

 What is the size of the standard envelope ?

It depends on what you mean by "standard envelope". Do you talk about the classical size of envelopes you receive everyday by post ? In this case, it can be the DL envelope 11 x 22 cm which is well-spread to send professional letters, or the C6 envelope 11.4 x 16.2 cm which is used to send non-professional letters.

cardboard envelope
Cardboard envelope

2. The different types of envelope

There are several types of envelopes excluding the standard envelope. Here there are:

· Paper business envelope

This is the most common envelope, the one we receive everyday in our letter box to get an invoice, a pay slip, etc. It follows the international standards which are explained above.

· Kraft envelope

The kraft envelope is made of kraft paper and is bigger and tougher than the business envelope. Indeed, the kraft paper has a strong resistance to tear and wear. That's why it is often used to send important documents such as an application file or an administrative form.

· Bubble envelope

This is a padded envelope with bubble wrap inside in order to protect fragile goods. The air bubbles absorb the shocks during all the transit while the kraft paper on the outside keeps the envelope intact.

· Cardboard envelope

Entirely made of cardboard, this envelope can carry books, magazines or other important documents without folding them. It is very thick in order to protect the content from bumps and knocks.

· Board backed envelope

The board backed envelope has one side in kraft paper and one side in stiff cardboard. Its goal is to send documents without folding them just like the cardboard envelope. But, it can only contain papers.

· Plastic mailing bag for the distance selling

The plastic envelope is well-known to be waterproof and tearproof. No one can open it without getting notice! So, it is very used by the distant sellers to ship clothing.

Important: we are talking about "envelope" when the opening is on the longest side and "bag" when the opening is on the smallest side.


See our full range of envelopes


opaque plastic mailing bag
Opaque plastic mailing bag

3. How to choose the right envelope?

When you buy an envelope, you have to choose between different sizes but also between different characteristics. There are 4 characteristics: the sealing, the basis weight of the paper, the presence of a window, the presence of a gusset.

· The sealing

The choice of the sealing is very important because it ensures the closing of your envelope. So, you have to choose the envelope which is quick but also effective to close. The sealing needs to last during transport. There are three types of sealing:

  • gummed sealing flaps: to activate the adhesion process, you need to moisten the layer of adhesive along the envelope flap in order to allow the gum to glue the flap closed. This is the most common and the cheapest sealing; it can be closed manually or automatically by a mailing machine.
  • self-seal flaps (or "press & seal flaps"): to activate the adhesion process, you just need to press the two flaps together. Both have a strip of latex, so when they are pressed together, they form an instant bond. This is the fastest sealing which is efficient for occasional shipping but also for large-scale shipping.
  • peel & seal flaps (or "strip seal"): to activate the adhesion process, you just have to peel away the strip which protects the latex adhesive and press down to form an instant bond. This is the simplest and the most secure sealing. Perfect to send letters daily!

· The basis weight

There are 4 different basis weight for the paper of the standard envelopes:

  • 80 g: standard basis weight for the daily shipping, the cheapest model
  • 90 g: best value of money with a better basis weight at a low cost
  • 100 g: basis weight used to send the most prestigious letters, for the brand image of your company
  • 120 g: basis weight used to send heavy or voluminous letters which need an efficient protection

· The window

The window has just one goal: helping you to save time. You don't need to write the name of the recipient on the envelope because it is shown through the window! It is mostly used to send business letters; you send generally many letters at the same time.

Warning: the majority of the envelopes with a window can't be recycled because of the plastic of the window. Only the envelopes with the NF certification can be entirely recycled because their windows are made of clear paper.

· The gusset

The gusset allows you to expand the thickness of your envelope in order to contain voluminous documents stored in a binder or to contain a book. The size of the gusset varies from 3 to 9 cm, so you can put all the documents you want inside!