How Many Stamps Do I Need for a Large Envelope?

If you’re sending a large envelope in the mail, you’ll need to make sure you’ve purchased the proper amount of postage for it. Postage covers the weight of letters, with one Forever stamp accounting for the first ounce of an envelope’s weight. If your large envelope weighs more than one ounce, you’ll need more than one postage stamp in order for USPS to accept it.

The Amount of Stamps You Need for a Large Envelope Depends on How Many Ounces the Envelope Weighs

Like most rules in the shipping and mailing industry, the amount of stamps you need for a large envelope depends on how many ounces your envelope weighs with all the contents inside of it. Most large envelopes containing documents that USPS delivers weigh one ounce or less. Therefore, most manila and large envelopes only require one Forever stamp to send them.

That said, there are often cases where a large envelope weighs more than just one ounce. A letter covered by First-Class stamps can be up to three ounces, and if your letter weighs more than one ounce, you’ll need to pay for the “Additional Ounce” postage to cover each additional ounce up to three ounces total. These stamps don’t cost the full 58 cents, but only 20 cents per each additional ounce. If you’d like to see some examples of “Additional Ounce” postage, you can check out these stamps on the USPS website. You can also pick up Additional Postage stamps for 5 or 10 cents each, but in our experience, if you need to pay for an extra ounce, it makes the most sense to just spring for the Additional Ounce postage stamps.

Pro Tip: If your large envelope weighs three ounces, you can technically use three Forever stamps to cover the full cost of postage, too! You’ll be paying a little more than you have to, but USPS will accept the letter, no questions asked.

Make Sure Your Envelope isn’t a Poly Mailer

Here’s something important to remember when loading up your envelope with stamps: make sure you’re in fact sending an envelope and not a poly mailer! USPS considers large envelopes (like manila envelopes) as “Flats,” and you can only purchase First-Class postage to send Flats in the mail. Poly mailers, on the other hand, are more three-dimensional envelopes that USPS requires you to use a shipping service for, such as First Class Package or Priority Mail.

The best way to determine if USPS will classify your envelope as a “Flat” is to double-check its measurements. For USPS to consider a large envelope a Flat for mailing, your envelope’s dimensions must be:

• A minimum of 5” x 3.5”
• A maximum of 11.5” x 6.125”
• No thicker than 1/4″

If your envelope fits within those parameters, then you’ll need to mail it and not ship it!

Sending Envelopes is Different from Sending Postcards

Another thing to keep in mind is that the postage for a manila envelope is much more expensive (percentage-wise) than the cost of postage to send a postcard. Postcard stamps are only $0.40 each, while the cost of a regular Forever First-Class stamp is $0.58.

You can technically use a Forever Stamp to send a postcard, since $0.58 more than covers the fee…although you’ll be overpaying by $0.18. If that matters to you, then you can order postcard stamps directly off the USPS website, or you can get some at your local Post Office.

On the other hand, if 18 cents won’t move the needle all that much, you can keep a roll of Forever stamps handy and use them for all of your mailing needs…whether you’re sending letters, large manila envelopes, or postcards.