Envelope Styles & Sizes
There are various parts of an envelope. Variations of these parts create different envelope styles.
The envelopes with the opening and seal slap located on the short dimension are called Open End envelopes. The ones with the flap on the long dimension are called Open Side envelopes. These envelopes are ideal for automatic insertion applications.
Remember, not all envelopes are machine friendly. When you choose an envelope that is machine friendly, you save time and money. If you are unsure, please call PDM to discuss.
Flap Styles

The flap is the part of the envelope that is folded to seal it. The main flap shapes are shown.

Remember, certain flap shapes and sizes can make an envelope not machine friendly. As always, if you are unsure, please call us at PDM to discuss.

There are two main envelope standard systems. The first is used in Buffalo, Pittsburgh, and the rest of the United States. (US envelopes are often referred to as Standard.) The other is the ISO metric system used in Europe and other parts of the world.

Envelope sizes vary. Listed are a few of the most commonly used sizes. (Sizes are listed in inches.)

These are common envelopes used for announcements, invitations, cards, small booklets, brochures, or other promotional pieces. Flaps are usually pointed or flat.

These are more formal, deeper envelopes used for announcements, invitations, and cards. Flaps are usually pointed.

These envelopes are often used for sending catalogs and folders.

These envelopes are mainly used for sending catalogs, magazines, and reports.

There is also metal clasp, coin, and other styles not listed here, because they are typically not suitable for printing.
Window envelopes are most often used for bills, checks, and marketing purposes. They are very cost efficient since the name and address shows through the window, eliminating the need for additional printing of the address on the envelope.

The sizes and positions of windows vary greatly depend on the manufacturer.


The most common window size (and recommended by the USPS) is 1-1/8 x 4-1/2, and the position is 7/8 inch from the left and 1/2 or 5/8 inch from the bottom.

These envelopes are often used for checks and invoices. Check, #9 and #10 are the most popular sizes.

For more information or if you have any questions, please reach out to us today!
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