For current postage and shipping rates go to USPS Price List.
To qualify for mailing at the First-Class Mail postcard price, it must be:
- At least 3-1/2 inches high x 5 inches long x 0.007 inch thick
- No more than 4-1/4 inches high x 6 inches long x 0.016 inches thick
If your mailpiece does not meet the dimensions above, then the Postal Service considers it a letter and letter-size postage is charged.
To be eligible for mailing at the price for letters, a piece must be:
- At least 3-1/2 inches high x 5 inches long x 0.007 inch thick.
- No more than 6-1/8 inches high x 11-1/2 inches long x 1/4 inch thick.
First-Class Mail letters that have one or more nonmachinable characteristics will pay a nonmachinable surcharge. Customers can be unpleasantly surprised that they must pay extra postage when, for example, they mail a square greeting card. The Postal Service charges extra postage because mailpieces that are rigid, square, or unusually shaped, often jam postal equipment and are difficult to process.
Examples of a nonmachinable letter include:
- It has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5 (a square envelope has an aspect ratio of 1, making it nonmachinable).
- It is more than 4-1/4 inches high or more than 6 inches long and is less than 0.009 inch thick.
- It has clasps, strings, buttons, or similar closure devices.
- It is too rigid.
- It has a delivery address parallel to the shorter side of the mailpiece.
- It contains items such as pens, pencils, or keys that create an uneven thickness.
Large Envelopes and Flats
The Postal Service uses the word “flats” to refer to large envelopes, newsletters, and magazines. The words large envelopes and flats are used interchangeably. Whatever you call them, flats must:
- Have one dimension that is greater than 6-1/8 inches high OR 11-½ inches long OR ¼ inch thick.
- Be no more than 12 inches high x 15 inches long x ¾ inch thick.
* Large Envelopes exceed one or more of the letter size maximum dimensions.
The maximum size for a flat provides plenty of room to put lots of material in the envelope. But keep in mind that weight usually affects price– the higher the weight the higher the postage, especially for First-Class Mail.