Envelope Sizes and Types
The size of the envelope should properly accommodate the contents. In the US Postal System, there are two categories of envelopes: Letter size and Flats.
Letters, non-letters, and bar-coded flats are rated differently by the USPS. To assure the best rate, call Mail Services for size and rates before preparing the mail piece. Use light colored envelopes for legibility, and please avoid brilliant colors (especially Red).
Letter Size
Letter size mail must be rectangular in shape for automated processing by the US Post Office.
To ensure prompt and efficient processing of First-Class mail, it is recommended that all envelopes and cards:
1. Have an aspect ratio (length divided by height) between 1 to 1.3 and 1 to 2.5 inclusive. See Mail Services for envelope template if you are not sure of the sizing.
2. Be sealed or secured on all four edges so that they can be handled by machines
3. Meet the following dimensions for automated processing by the USPS:
Height
3 1/2" Min
6 1/8" Max
Length
5" Min
11 1/2" Max
Thickness*
.007 Min
1/4" Max
Note: Maximum thickness for automated processing is 1/4". Mail that does not meet automated processing size may not qualify for discounted rates. Letter size envelopes (up to 6 1/8" x 11 1/2") over 1/4" thick will be returned to originator for re-enveloping.
Window Envelopes
Enclosures that are designed so that the address appears in a window should not be stapled or glued in place. If the addressed enclosure does not properly fit inside the window, use an envelope without a window.
Non-Letter (Flats)
Non letter size envelopes are larger than the maximum letter size, but not larger than 12" high by 15 3/4" and 1 1/4" thick.
International Letter Size Envelops
Mail to be sent outside of the United States should be separated from all First Class mail and flagged with a Post It note to insure proper postage is applied.
NOTE: The last line of any foreign address should be the country name spelled out in capital letters, in English.
Bar-coded Flats
The Postal Service allows discounts for bar-coded flats. Please contact Mail Services for details and current rates.
Plain White or Manila Envelopes
Both of these types of envelopes can be used for all other classes of mail. These should be marked to show the proper class of mail, (i.e., First Class or Standard Mail).
Padded Envelopes
These envelopes contain a cushioned lining to provide a degree of safety for mailing small and fragile merchandise. These are available from Mail Services upon special request. We also stock computer diskette mailing envelopes.