How Many Stamps Do I Need for 3 Oz Packages? (USPS)

Whether you’re sending some legal documents in a manila envelope, or a delicate figurine in a bubble mailer, one thing remains the same- you’ve got to know how many stamps to put on your 3-ounce mailpiece.

It may seem like an easy answer at first, but you’ve got to consider the size and shape of your item when estimating your shipping costs.

Therefore, in this article, we’ll help shed some light on how much you can expect to pay, and how many stamps you’ll need, so keep reading!

How Many Stamps Do I Need for 3 Oz Packages at USPS In [currentyear]?

At the current rates, a 3-ounce letter costs $0.98, and requires 1 Forever Stamp and 2 additional ounce stamps. Larger envelopes weighing 3 ounces cost $1.56 to mail, and require 1 Forever Stamp and 1 3-ounce stamp. A small package weighing 3 ounces costs $4.50 to send, and requires 8 Forever Stamps.

If you still don’t know how many stamps to put on your 3-ounce mailpiece, then don’t worry, we’ve got all of the answers here!

How Many Stamps Do I Need for a 3 Oz Envelope?

If you’re mailing a standard-sized envelope* that weighs between 2.1 and 3.0 ounces, you’ll need to provide $0.98 worth of postage at the current rates.

There are a couple of different ways you can pay for this postage, so let’s look at them in more detail:

  • One 3-ounce stamp (currently priced at $0.98)
  • One domestic Forever Stamp, 2 additional-ounce stamps (Total = $0.98)

*According to USPS, standard-sized letters are those that are rectangular in shape, and fall within these dimensions:

At least 3 ½ inches high x 5 inches long x 0.007 inch thick, but not more than 6 ⅛  inches high x 11 ½  inches long x ¼  inch thick.

How Many Forever Stamps Do I Need for a 3 Oz Letter?

USPS’ 3-ounce stamps are like standard Forever Stamps, in that they will always cover the postage for 3-ounce letters, regardless of any changes to postage rates in the future.

In other words, one 3-ounce stamp will always be enough to mail a 3-ounce letter.

If you don’t have any 3-ounce stamps laying around, you’ll need one “standard” Forever Stamp, plus 2 additional-ounce stamps to cover the postage of a 3-ounce letter.  

Alternatively, you could use 2 Forever Stamps to mail a 3-ounce letter.

We don’t recommend this option, because at current rates ($0.58), you’d be paying $1.16 to mail a letter that only costs $0.98 to mail.

Put another way, you’d be paying $0.18 more than you need to. 

How Much Postage Do I Need for a 3 Oz Flat?

How Much Postage Do I Need for a 3 Oz Flat? USPS

USPS classifies and prices large flat envelopes (also known as flats) differently from smaller envelopes.

Here are the criteria USPS uses to define flats:

  • A rectangular mailpiece no thicker than ¾ inch
  • No larger than 15 inches x 12 inches x ¾ inches thick
  • Weighs less than 13 ounces
  • Must be flexible
  • Uniformly thick (i.e. no bulges or bumps)
  • Have four square corners (or finished corners not exceeding a radius of ⅛ inch thick)

For 3-ounce flats, USPS currently charges $1.56.

You can pay this postage in a few different ways:

  • 1 3-ounce stamp and 1 Forever Stamp (Total = $1.56)
  • 1 3-ounce stamp and 3 additional-ounce stamps (Total = $1.58, you overpay by $0.02)
  • 3 Forever Stamps (Total = $1. 74, you overpay by $0.18)

How Many Stamps Do I Need for a 3 Oz Manila Envelope?

How much postage you need for a manila envelope depends on its size and weight.

Standard-size manila envelopes are 9 inches x 12 inches. As a result, USPS classifies and prices them as large envelopes/flats.

At the current rates, 3-ounce manila envelopes ship for $1.56. We discussed different ways to pay for this postage in the previous section.

That being said, if you’re using a manila envelope for business or legal purposes, we don’t recommend using postage stamps unless you’re really in a pinch.

Rather, bring your envelope to the post office, and have an associate print your postage (called metered postage).

Not only can metered postage help your envelope get delivered more quickly, but it also ensures that you don’t under or overpay on postage.

What’s more, it looks much more professional than sticking a hodge-podge of stamps to your envelope.

How Many Stamps Do I Need for a 3 Oz Bubble Mailer?

USPS bases postage prices for bubble mailers on their size and weight.

If a bubble mailer is less than ¾ inch thick, then it’s priced like other large envelopes/flats. If it’s thicker than that, USPS classifies it as a parcel, and it’s priced differently.

For 3-ounce bubble mailers that meet the criteria to be considered flats, expect to pay $1.56 (see the above sections). 

For 3-ounce bubble mailers that are thicker than ¾ inch, you will pay the First-Class Package rate, which is currently priced at $4.50.

Here are a few ways to pay for your bubble mailer package with stamps:

  • One $5 definitive stamp (Total = $5.00, you overpay by $0.50)
  • Two $2 definitive stamps and 1 Forever Stamp (Total = $4.58, you overpay by $0.08)
  • 8 Forever Stamps (Total= $4.64, you overpay by $0.14)

While it’s possible to pay for a bubble mailer using stamps, it’s not recommended. That’s because there’s a pretty good chance that you’ll either under or overpay.

Therefore, your best option is to take your bubble mailer to a USPS clerk, and have them print metered postage for you.

To find out more, you can also read our posts on how many stamps per pound, how many stamps are needed per oz, and USPS stamp types.


The amount of postage you owe depends on how big your envelope is. For small 3-ounce envelopes, you’ll typically pay $0.98. For large envelopes/flats, your starting price is $1.56. If you’ve got a thick bubble mailer, then expect to pay $4.50.

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Marques Thomas

Marques Thomas graduated with a MBA in 2011. Since then, Marques has worked in the retail and consumer service industry as a manager, advisor, and marketer. Marques is also the head writer and founder of

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