How Many Stamps Do You Put on a 9x12 Envelope?

By Staff WriterLast Updated Jul 15, 2020 12:28:31 PM ET
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Picture Courtesy: [Didgeman/Pixabay]

A 9x12 envelope is considered a large envelope according to the mailing standards of the United State Postal Service (USPS). This means that it will require more than one stamp to mail. Instead, you must use the weight of the envelope to determine how many stamps it needs. You can use two First-Class stamps to mail a 9x12 envelope with a weight up to an ounce.


Adding Postage to 9x12 Envelopes That Weigh More Than an Ounce

The USPS charges $1.00 in postage for 9x12 envelopes that weigh up to an ounce. Two $0.55 First-Class stamps provide enough postage in this situation. However, if your envelope weighs more than an ounce, you’ll need to add $0.15 in postage for each additional ounce.

Assume that your 9x12 envelope has a weight of four ounces. The additional three ounces of weight mean that you’ll need an additional $0.45 of postage. This four-ounce letter requires three First-Class stamps to cover the additional postage. 

Paying for Postage on a 9x12 Envelope 

Though it’s perfectly acceptable to use stamps for postage on your 9x12 envelope, this isn’t your only option for postmarking the envelope. An alternative is to weigh the envelope using a postage meter, and then paying the appropriate amount of postage for its weight. Some individuals prefer this option so that they don’t have to “waste” a stamp for a few cents worth of postage. 

For example, imagine that you need to mail a 9x12 envelope with a weight of six ounces. The additional five ounces requires an additional $0.75 worth of postage, for a total postage of $1.75. If you use three First-Class $0.55 stamps, this is $1.65 worth of postage. You’ll need to use another $0.55 First-Class stamp to cover the remaining $0.10 of postage. 

Instead, you can have your envelope weighed at your local post office, where you can then pay the correct amount of postage. If you have your own mail scale, you can weigh the envelope and pay for your postage online using a third-party mail service. Then, just put the envelope in your mailbox and put the flag up or hand it directly to your mail person.  

Other Factors That Can Influence the Price of Your Envelope’s Postage

Occasionally, you’ll need to remit additional postage for your 9x12 envelope. The previously stated postage rates assume that your envelope has a regular shape and can easily be sorted via a machine. However, if the envelope is lumpy or has an irregular design, it’ll need to be sorted by hand, even if it weighs less than an ounce. This means that you’ll need to pay a special handling surcharge that will increase the price of your postage. 

Items That You Can Mail with a 9x12 Envelope

One of the reasons that a 9x12 envelope is a popular mailing alternative is that it accommodates a variety of items. Some items that you can mail using a 9x12 envelope include:

  • Books
  • Magazines
  • CDs
  • DVDs
  • Documents
  • Catalogs
  • Manuscripts
  • Photos
  • Artwork


Whatever you mail in the envelope should have a uniform thickness so that the envelope maintains an even shape.

Faster Mailing Options for Your 9x12 Envelope

Though First-Class mail is an affordable option for mailing your 9x12 envelope, it isn’t the fastest alternative. Items sent via First-Class mail take an average of one to three business days to reach their destination. If you want your envelope to arrive at its destination as quickly as possible, consider upgrading your postage to 2-Day Priority Mail. A 9x12 envelope will fit in a flat-rate Priority Mail envelope that ships for $7.35. Want it to get there even faster? Sent it Priority Mail Express for a flat rate of $25.50.