They are charged a nonmachinable surcharge even if they weigh less than 1 oz. Unusually shaped mail, like square or vertical envelopes, lumpy envelopes, rigid envelopes, and mail with clasps, string, or buttons, must be hand-canceled. Additional size restrictions apply depending on the type of mailpiece you're sending.Īdditional Charges for Irregular Mailpieces & Envelopes Nonmachinable Envelopes All postcards and envelopes (or flats) must be rectangular, otherwise an additional charge may apply.Maximum weight for First-Class Mail letters is 3.5 oz for large First-Class Mail envelopes, the maximum weight is 13 oz.Large envelopes (flats) start at $1.35.Oversized postcards need letter stamps, which start at $0.66.Standard-sized, rectangular postcard stamps start at $0.51.Square, oversized, or unusually shaped envelope stamps start at $1.06.

Standard-sized, rectangular envelope stamps start at $0.66.

Standard Letter & Postcard Sizes See Insurance & Extra Services Letters

One price for up to 3.5 ounces with commercially priced letters and cards.

Eligible for Delivery Confirmation ™ services such as Certified Mail ®.

Flat Rate envelopes can also be used for international shipments, to do so use the International window to print postage, addresses and customs forms in one swift operation.

The easiest way to print postage for flat rate envelopes is to use the Packages window to print out shipping labels - print addresses, postage and tracking information in one easy step and save up to 11% on Priority Mail and 3% on Priority Mail Express.

You can fill them with as much material as desired, so long as the flap of the envelope closes securely and the weight does not exceed 70 pounds for domestic mailings or 4 pounds for international mailings. To order free USPS Flat Rate Envelopes or any other free Priority or Priority Mail Express supplies go to the Store. supports the following USPS Flat Rate Envelopes:

Best of all they are free and also are more likely to get your documents to their destination faster than when using your own envelope (due to the fact that the envelopes are highly recognizable as Priority or Priority Mail Express). Looking to send documents using Priority or Priority Mail Express and want to make sure you are paying the lowest rates? The USPS has pre-printed flat rate envelopes that you can use to send your documents across the nation or across the world for one low flat rate, regardless of weight or distance.

Usps priority padded flat rate envelope