How Much Does It Cost to Mail a 9×12 Envelope? [9×12 Postage Cost]

The United States Postal Service changed the price of mailing a 9×12 envelope in January 2021. So, now, how much does it cost to mail a 9×12 envelope?

The cost of mailing a 9×12 envelope will depend on its weight. Prices start at $1.00 and increase by $0.21 for every additional ounce. The USPS considers this envelope as a large envelope.

If you have an envelope this big, you don’t need to visit the Post Office to mail it. As long as you have access to a postage meter, or you have postage stamps, or you can print postage online from companies such as

Read on to learn more about the cost of mailing a 9×12 envelope, how many stamps it requires, and the factors that affect the mailing cost.

How Much Does It Cost to Mail a 9×12 Envelope?

how much does it cost to mail a 9x12 envelope

To calculate the cost of mailing a 9×12 envelope, you have to consider its weight and not just its envelope size. The price starts at $1.00. This will increase by $0.21 for every ounce that you add to the envelope.

The USPS considers the 9×12 envelope as a large envelope. You don’t have to visit the Post Office to mail such kind of envelope as long as you have access to a postage meter or can print postage online from a website such as You can also stick postage stamps if you already know how many stamps are required.

In a 9×12 envelope, the first ounce requires two Forever Stamps. This is the equivalent of $1.00. Also, you have to pay extra if the envelope’s weight plus its contents exceed one ounce. For each additional ounce, you have to pay $0.21.

Actual Cost Depends On Several Factors

If the envelope’s contents are just a few sheets of paper, the envelope will have a uniform thickness. It will be bendable as well. The price will most likely be just the minimum, which is $1.00. It seems that you can have a maximum weight of 13 ounces that you can put inside this envelope size. Just multiply the number of additional ounces by $0.21 to get the total cost.

The envelope’s destination does not influence the cost as long as it is First Class Mail and its weight is no more than 13 ounces. If the 9×12 envelope is not lumpy and not inflexible, it is considered First Class Flat.

Aside from the weight, other factors will influence the cost of a particular 9×12 envelope. Here are some of these factors:

1. The Envelope Is Lumpy and Inflexible

If the envelope is inflexible and lumpy, it will be classified as First Class Package. Postage for this type of mail is $3.50 with a maximum weight of 4 ounces. The following table will show you the cost of 9×12 envelope postage if the envelope’s weight exceeds 4 ounces.

Maximum WeightCost of Postage
8 ounces$3.75
9 ounces$4.10
10 ounces$4.45
11 ounces$4.80
12 ounces$5.15
13 ounces$5.50

2. The Envelope Is Hard but Light

If the envelope is stiff but still light, the Post Office may require more Forever stamps. Envelopes could be stiff if they contain Styrofoam filler. They will be considered as a First Class parcel. Most likely, this kind of envelope will need five Forever stamps.

Forever stamps are so-called because you can use them forever. Ordinarily, they are non-denominated, or they don’t have value on their face. The word forever is written on the stamp with a diagonal strikethrough. Currently, they are worth $0.50.

3. Thickness of the Envelope

If the 9×12 envelope is thick, the cost of postage will increase. If it is about 1/4 inch thick, the envelope is still considered ‘flat.’ But if the thickness of the envelope approaches 3/4 inch, or if there are more than 1/4 inch variations in the envelope’s thickness, it will be considered a parcel. The envelope’s postage will be $4.10.

4. The Envelope Is Not Fully Flat

If the envelope is not completely flat, you will likely pay more for postage. The additional cost is that postal workers need to sort these kinds of mail by hand instead of just running them through postal machines.

Postal machines automatically sort flat envelopes. This makes the process easier and faster, and not too many hands are needed. But inflexible and lumpy envelopes have to be manually sorted. This process adds more labor and time to the sorting out process. That is why non-flat envelopes need more postage.

5. Size and Shape Affect Postage Cost

There are different postage costs for different types of mails. The different types of mails include letters, postcards, large flat envelopes, and parcels. Generally, the bigger the mail, the higher is its postage fee.

When it comes to First Class mails, postage for letters is higher than postage for postcards. Large flat envelopes need more postage stamps than letters. The highest of the bunch is parcel mails or boxes because of their processing and delivery costs.

9×12 Mail Is Classified as a Large Envelope

postage for 9x12 envelope

As per the USPS, a 9×12 envelope is a large envelope. This term is also known as flat mail. It is a classification given to envelopes that are more than 6 1/8 inches high, 11 1/2 inches wide, and 1/4 inch thick.


Most of these envelopes are used for mailing legal correspondence, product catalogs, and marketing newsletters. Some people are also using this size envelope to mail magazines, documents, reports, manuscripts, CDs, and even books. But to be considered ‘flat mail,’ the thickness of the envelope must be uniform.

These envelopes are oftentimes used to mail unfolded documents in sheets of 8 1/2“x 11” bond paper. The thickness of the envelope must not exceed 1/4 inch. Its height should not be more than 12 inches, and its width not more than 15 inches. The total weight of the envelope, including its contents, must not exceed 13 ounces.

If the envelope exceeds any of these flat mail parameters, the USPS will consider it a package. The postage rate that it will be subjected to is the parcel prices. Note that they will charge you $0.21 per ounce of additional weight.

What Are the Things You Need to Send an Envelope?

In sending large envelopes, you don’t need to visit the Post Office. But you need to have access to any of these three things:

  • Postage meter,
  • Postage stamps, or
  • Online printing of postage from companies like

If you have access to any of these three, you only need to address your envelope, attach the correct amount of postage on the envelope’s upper right corner, and hand it to your local mail carrier or drop it in the nearest post office collection box. Your recipient will receive your envelope within 3 working days.

Again, how much does it cost to mail a 9×12 envelope? The cost to mail a 9×12 envelope is a minimum of $1.00 and increases by $0.21 for every additional ounce. The USPS considers this envelope as a large envelope.

How Many Stamps Are Required for a 9×12 Envelope?

The 9×12 envelope is the standard large envelope accepted by the USPS. Like a standard letter, this envelope requires postage stamps affixed at the top right corner to be provided proper postal service.

You can affix two First Class stamps to mail your 9×12 envelope if its total weight does not exceed 1 ounce. The USPS requires $1.00 worth of postage for this size’s envelopes that weigh no more than 1 ounce.

One First Class stamp has a value of $0.55. But you are only required to pay $1.00 if your 9×12 envelope does not weigh more than 1 ounce. The explanation for this is that you are paying the extra $0.10 for its convenience.

If your 9×12 envelope contains things that make it heavier than 1 ounce, the postage will be more than $1.00. Say your envelope weighs 4 ounces. That is 3 ounces more than the minimum. So, you will add three more stamps. At $0.55 per stamp, that will be $1.65. Add that to the $1.00 minimum price, and the total postage is $2.65.

If you want to get an accurate postage cost for a 9×12 envelope, there is a USPS postage calculator that you can use. It is available on their official website.

Faster Mailing Options For 9×12 Envelopes

The standard postage costs for large flat envelopes will deliver your mail within three working days. What if you want your mail delivered faster than that? There is an alternative that is faster than the First Class stamp route.

The USPS offers the Priority Mail Express 2-Day service. If you choose this option, the USPS guarantees that your mail will get to its destination within two days of mailing. Or it could be the faster same-day delivery. Of course, there is a higher price tag for this express mail service.

 Ordinarily, your flat large envelope will cost you $1.00 to ship. But if you choose express mail service, you will be paying USPS $26. But this is still a good alternative considering that the USPS is handling almost 500 million pieces of letters, envelopes, and parcels each day. And it’s worth considering if the other party needs your document as early as possible.

USPS’ Priority Mail Express charges for large flat envelopes are the following:

  • For 9 1/2″ x 12 1/2″ Flat Rate Envelope – $26.35
  • A 9 1/2″ x 15″ Legal Flat Rate Envelope – $26.50
  • For 9 1/2″ x 12 1/2″ Padded Flat Rate Envelope – $26.95

Things You Can Mail Using 9×12 Envelopes

9x12 envelope postage

This envelope size is very convenient for shipping different types of items. Usually, here are the items inside an envelope this size:

  • Manuscripts
  • Photographs
  • Small artwork
  • Books
  • Video game discs
  • DVD and Blu-ray discs

Most of these items are flat, which is why the 9×12 envelope is ideal for sending them through the mail. If you use boxes to send these items, you will be buying more postage stamps. But be sure to flatten the 9×12 envelope so that the post office machines can process it instead of manually sorted.

Here Is an Easy Option Using

There is an easy option of sending your 9×12 envelope through USPS. You can use instead of computing your postage and sending the mail yourself. is a company based in California, USA. This company offers internet-based mailing and shipping services.

With, sending your large envelopes through the mail is very easy. They will compute the amount of postage you need to pay. You don’t have to go to your local post office to mail your envelope. has a system that allows you to print postage and address labels from the comfort of your home or your office. The USPS officially authorizes these postage stamps and address labels. They will be honored by any Post Office in the country or the country where you are sending your envelope.

If you send mail to an international destination, this mailing service company will even allow you to fill out customs forms right through their computer interface. In that way, you can print postage, customs forms, and address label in a very convenient and easy way.

Conclusion: Postage for 9×12 Envelope

The actual cost of mailing a 9×12 envelope will depend on several factors. One of these factors is its weight. Mail costs start at $1.00, but it increases by $0.21 for every additional ounce. The USPS considers the 9×12 envelope as a large envelope.

As such, its mailing cost is higher than regular letter envelopes. Mailing costs will also increase according to the type of mailing services that you will choose. 

For your reference, here’s a table indicating how much is the postage cost depending on weight:

Maximum WeightCost of Postage
8 ounces$3.75
9 ounces$4.10
10 ounces$4.45
11 ounces$4.80
12 ounces$5.15
13 ounces$5.50