“How Many Stamps Do I Need?”


May 10, 2023

In 2022, USPS (United States Postal Service) printed 13.8 billion stamps and collected $4.2 billion from the sales of stamps and stamp products.

Stamps are necessary to send mail and prove you paid for its postage. But where can you buy stamps, and how many stamps do you need when sending letters, envelopes, and postcards? 

How many stamps should you use per ounce (oz) of mail or package? Under what conditions should you use more than one stamp?

This article discusses how many stamps you need when sending mail and covers the conditions under which you should use more than one stamp.

FindPostOffice.org aims to become the online post office locator of choice that offers helpful information about shipping and mailing, including details about stamps to use when sending mail or packages.

“How Do I Figure Out How Many Stamps I Need?”

When sending mail or parcels, consider the following points so that you can purchase the correct postage and number of stamps:

Size and Weight Determine Current Rates

Your envelope must be flat and fit through a piece of automated processing equipment. If not, USPS will consider your mail as non-machinable, which can cost more.

Non-machinable items include rigid (unbendable) or lumpy (not uniformly thick) envelopes and those with clasps, buttons, or strings. Unusually shaped envelopes will also cost extra to send.


To ensure that your envelopes pass the automated sorting process at the post office, consider the following reminders:

  • Your envelope must be made of paper.
  • Your envelope must be rectangular to qualify for letter prices.
  • Large envelopes must be rectangular to gain flat-rate pricing.
  • The post office can charge package prices for envelopes larger than letter size.
“How Many Stamps Do I Need to Send Large Envelopes?”

One Forever stamp covers the first ounce of your envelope’s weight. You can use Forever stamps to mail one-ounce letters regardless of when you purchased those stamps and how stamp prices change in the future.

For large envelopes weighing more than one ounce (1oz), you need more than one stamp for the U.S. Postal Service to accept your mail.

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

The number of stamps needed to send a large envelope depends on the weight of your envelope and its contents.

Most large envelopes that USPS delivers contain documents weighing 1oz or less. These envelopes require only one Forever stamp to send.

If a large envelope’s weight exceeds 1oz, you must pay additional-ounce postage to cover up to 3oz of each extra ounce.

Make Sure Your Envelope Isn’t a Poly Mailer

Poly mailers are plastic envelopes for three-dimensional items that require using a shipping service like Priority Mail or First-Class package to send.

Meanwhile, large envelopes like manila envelopes are flats. You can purchase First-Class postage to send flats in the mail.

“How Many Stamps Do I Need for a 9×12 Envelope?”

A 9×12 (9 inches by 12 inches) envelope is categorized as a “large envelope,” with postage at $1.26. This price is the equivalent of two Forever stamps at $0.63 each ($0.63 x 2 = $1.26).

This postage covers the first ounce only. You will need more stamps for each extra ounce of the envelope’s weight.

Sending Envelopes Is Different From Sending Postcards

One difference between envelopes and postcards is that the postage for sending envelopes is more expensive than sending a postcard. A Forever stamp costs $0.63 for envelopes, while postcard stamps are only $0.48 each.

Although you can use a Forever stamp to send a postcard, you will be spending more doing so based on the stamp prices. Instead, purchase a postcard stamp from your local post office or the USPS website.

Flats Requirements and Costs for Flats

You must use flats to ship documents weighing between 3.5oz and 13oz. These flats must meet the following requirements:

  • Dimensions must be at least 6.125 inches (in) by 11.5in and no larger than 12in by 15in.
  • The envelopes must not be thicker than 0.75in.
  • A bubble packet is not allowed as it makes the document thick.

Since flats are large envelopes, sending them costs $1.26 for the first ounce. For flats weighing more than 1oz, you must purchase additional-ounce stamps at $0.24 each.

How to Weigh Your Envelope

If you have a kitchen food scale, you can use it to weigh your envelope. If you do not have one, consider purchasing a basic scale, available in many online stores like Amazon. You can also go to your local post office to have your envelope weighed.


When sending postcards, consider the following pointers:

  • Postcards must be rectangular and have a standard size to qualify for First-Class Mail postage.
  • Oversized postcards are charged as letters or flats.

Standard postcard sizes are between 5in and 6in long, 3.5in and 4.25in high, and 0.007in and 0.016in thick.

Previous Price Increases

On January 22, 2023, the following price increases took effect:

ProductPrevious priceNew price
Letters (1oz)$0.60$0.63
Letters (metered 1oz)$0.57$0.60
Domestic postcards$0.44$0.48
International postcards$1.40$1.45
International letters (1oz)$1.40$1.45
Flat additional-ounce stamp$0.24$0.24

Non-machinable Characteristics

If your mail contains a wax seal, an external ribbon, a button, or other elements that make your mail rigid, you’ll likely pay a non-machinable surcharge. USPS charges $0.40 for this surcharge.

If you write the address sideways, the machine may not read the address correctly. Instead, the Postal Service will process the mail by hand and require a non-machinable surcharge.

How Many Stamps per Ounce?

The following sections discuss how many stamps you must purchase based on how many ounces your mail weighs.

“How Many Stamps for a 2-Ounce Letter Do I Need?”

A letter weighing 2oz will require the following stamps:

  • One domestic Forever stamp
  • One additional-ounce stamp

Sending More Than 3.5 Ounces or Sending Large Envelopes to the United States

If your envelope weighs more than 3.5oz, your postage will fall under flats weighing up to 13oz.

Price per Ounce

Whether your mail is a letter or flat, if its weight exceeds 1oz, you must buy a Forever stamp at $0.63 for the first ounce and additional postage at $0.24 per extra ounce.

USPS Changing the Rates of Its Postage Stamps

In its 10-year plan to achieve financial sustainability and service excellence, USPS announced numerous changes to the government service from 2021 to 2030. One of the plan’s goals is to earn a positive net income and a break-even operating performance over the next decade.

USPS implemented several changes to achieve this goal, including increasing the postage stamp rate.

“How Many Postage Stamps Do I Need to Send a Letter?”

The number of stamps required to mail letters depends on the following:

  • Weight of the letter
  • Size of the letter
  • Cost of the stamps
  • The class of the service, such as Priority Mail, Certified Mail, and First-Class Mail

Domestic Letter Shipping (Within the United States)

If you send mail within the U.S., whether the destination state is Texas, New York, Illinois or Hawaii, Alaska, and Delaware, your envelope must adhere to the following requirements to be eligible for mailing:

  • The envelope must measure at least 5in by 3.5in but at most 11.5in by 6.125in and no thicker than 0.25in.
  • The envelope must have a uniform thickness.
  • The envelope must be rectangular and bendable, or it will be non-machinable.
  • A square envelope is also non-machinable but must be at least 5in long.

Delivery Times for Letters to the United States

USPS does not provide a tracking service for stamped mail and does not guarantee delivery times. However, First-Class Mail usually arrives in one to five days and Priority Mail ships in one to three days.

Domestic Postcard Shipping (Within the United States)

If you send a postcard within the U.S., you must buy a postcard stamp and put the postcard in the mailbox. If the cost is negligible, you can also overpay your postage using a domestic Forever stamp.

“How Many Forever Stamps Do I Need?”

Typically, you only need one Forever stamp for the first ounce of your mail. If your letter weighs more than 1oz, you must purchase additional-ounce stamps instead of another Forever stamp. If you place more than one Forever stamp on your envelope, you will end up overpaying your postage.

“How Many Stamps Do I Need to Send Parcels in the U.S.?”

Calculating how many stamps you need for a parcel is more complicated than for letters because USPS charges parcel postage by the size, weight, and distance from the parcel’s origin to the destination.

Parcels are also usually too large to fit in a mailbox, so you must take them to a post office. You can then ask the post office staff to weigh your parcel and determine your postage.

How Many Stamps in a Book?

The standard postage stamp book contains 20 First-Class stamps that you can apply to envelopes and First-Class postage. You can also buy a Forever stamp book containing 20 stamps.

USPS also sells the Stamp Yearbook, a 64-page book released yearly containing designs and reference materials from the Postal Service’s stamp creation process.

Under What Conditions Do You Require More Than One Stamp When Sending Documents in the Mail in the United States?

In most cases, you will need more than one stamp if your mail weighs over 1oz. Aside from the weight, other factors to consider when determining the number of stamps include the service class and stamp value.

“What Can Happen if I Do Not Have the Right Amount of Stamps?”

If your mail has insufficient stamps and no return address, USPS will attempt to collect postage from the recipient.

If your recipient refuses to pay the postage and the mail has no return address, the Postal Service will consider the item a dead letter.

USPS processes these undelivered letters in a Mail Recovery Center (MRC), a facility that processes undeliverable and non-returnable mail.

Never Use Two Stamps

Some letters can be mailed with only one Forever stamp. However,  using two Forever stamps can waste money because they are more expensive than additional-ounce stamps for mail exceeding 1oz.

To ensure you do not overpay postage, use the USPS postage calculator to calculate actual postage rates.

What Can Happen When You Send Mail Without a Stamp?

As long as your mail has a return address, USPS will return the item so you can pay the correct postage and place the right number of stamps.

If your mail does not have a return address, the Postal Service will attempt to collect the postage from your recipient. But if they refuse to pay postage and the mail has no return address, USPS will send the item to the MRC.

USPS may eventually open the undelivered letter to check if a return address is inside. If there is none, the Postal Service will discard the mail permanently.

Where Can You Buy the Stamps You Need, and What Are the Postage Costs?

You can purchase stamps from your local post office or the Postal Store at USPS.com. Other places to buy stamps include grocery shops, gas stations, pharmacies, and licensed vendors like Stamps.com.


The postage for First-Class Mail letters starts at $0.63, and large envelopes start at $1.26. Each ounce exceeding the first ounce costs an additional $0.24.

Flat Rate Envelopes

As of April 2023, flat rate pricing for envelopes is as follows:

  • Priority Mail Express
    • Flat rate envelope: $28.75
    • Legal flat rate envelope: $28.95
    • Padded flat rate envelope: $29.45
  • Priority Mail
    • Flat rate envelope: $9.65
    • Legal flat rate envelope: $9.95
    • Padded flat rate envelope: $10.40

International Mail and Packages

As of April 2023, the following rates apply when sending mail to a destination outside the U.S.:

  • First-Class Mail International letters: Starts at $1.45 (1oz)
  • First-Class Mail International flats: Starts at $2.90 (1oz)
  • First-Class Package International Service: Starts at $15.75 (1oz to 8oz)

How to Send a Domestic Letter or Postcard

USPS provides a convenient way to send mail (letters, cards, and postcards) to domestic locations, including U.S. territories and military bases. The following sections provide a step-by-step process to send mail domestically:

Step 1: Choose an Envelope or Postcard

Use an envelope to send flat, flexible items like letters, cards, forms, checks, and other paper products. You can send a 1oz item, estimated to be about four sheets of regular, letter-sized (8.5in x 11in) paper in a rectangular envelope, to anywhere within the U.S.

USPS requires envelopes to be rectangular and made of paper to qualify for letter prices. If you must send unfolded letter-sized documents, consider using flats.

You must pay the package price if your envelope is nonrectangular, rigid, or lumpy.

If you send postcards, you do not have to put them in an envelope. Instead, you can use a postcard stamp and save money on postage since this stamp costs $0.48 only.

Step 2: Address Your Mail

When addressing envelopes, write the return or sender address in the top left corner and the delivery or recipient address in the bottom center.

For postcards, write the delivery address in the space provided, usually on the same side where you write your message and place the stamp.

Whether you are sending envelopes or postcards, always print your return and delivery addresses clearly and in the correct places to ensure the Postal Service delivers your mail on time.

Address Format

Format your address in the following manner:

  • Print or write addresses neatly and in capital letters.
  • Use a pen or permanent marker.
  • Do not use periods or commas.
  • Include the ZIP+4 Code (the ZIP Code plus four extra numbers) whenever possible.

Write Recipient Address

The recipient address in the envelope or postcard must include the following lines:

  • Recipient’s full name or company name
  • Apartment or suite number
  • Complete street address
  • City, state, and ZIP+4 Code

Write Sender Address

For the return address, write the following lines in the top-left corner of the envelope:

  • Your full name or company name
  • Apartment or suite number
  • Complete street address
  • City, state, and ZIP+4 Code

Special U.S. Addresses

If your destination address is a U.S. territory, APO (Air/Army Post Office), FPO (Fleet Post Office), or DPO (Diplomatic Post Office), follow the address guidelines below:

Puerto Rico

Some Puerto Rico addresses include a community or urbanization code for a specific area. For destinations with an urbanization code (URB), you should write the address using the following example:

SAN JUAN PR 00926-3232

U.S. Virgin Islands

When addressing mail to the Virgin Islands, use “VI” for the territory abbreviation, not “USA VI” or “US VI,” and follow the format below:

RR 1 BOX 6601
KINGSHILL VI 00850-9802


If you mail to a military or diplomatic address in another country, do not include the country or city name in the address line. Excluding this information helps keep your mail away from foreign mail networks.

Also, include the unit and box numbers that your recipient is assigned. Follow the format below when sending mail to an APO/FPO/DPO:

UNIT 100100 BOX 4120
FPO AP 96691

Step 3: Calculate and Apply Postage

Use the USPS postage calculator to determine how much you must pay to send your mail. If your envelope weighs 1oz, use a First-Class Mail Forever stamp, which costs $0.63, and place it in the envelope’s upper right corner. If you have other stamps, you can combine them to add up to $0.63.

You must pay additional fees if your mail is heavier, bigger, or needs insurance or extra services like Certified Mail.

If you send a standard postcard, the postage is $0.48. However, it can cost more if you use large or square postcards. Put the postcard stamp in the space near the delivery address.

Paying for Postage and Calculating Postage at the Post Office

Consider the following elements when you are calculating and paying for the postage price:

  • Destination
  • Speed
  • Shape and size
  • Special handling and insurance
  • Delivery confirmation receipts

Using a Postage Calculator

When calculating the price for sending mail, consider using the postage calculator on the USPS website. Depending on your destination, you may have to input the origin and destination ZIP codes, item value, and mailing date and time.

Postage Options

You can purchase postage stamps in the following locations:

  • The Postal Store: Shop online for stamps and add-on postage for heavier or oversized envelopes.
  • Post Office locations: Purchase stamps at post offices, self-service kiosks, or USPS-approved postal providers like drug stores and groceries.
  • Click-N-Ship: Pay for and print postage online if you send flats using Priority Mail Express or Priority Mail.

Step 4: Send Your Mail

After you place the correct addresses and postage on your envelope or postcard, send your mail by putting it in your mailbox or dropping it at a Post Office or blue collection box.

International Letter Shipping

One way to ship letters from the U.S. to other countries is to use Global Forever stamps. These stamps cost $1.45 each, and you can purchase them in sheets of 10 for $14.50 from the Postal Store.

You can also use domestic Forever stamps for international shipping, but the postage must add up to $1.45.

Because each domestic Forever stamp costs $0.63, buying two is insufficient ($0.63 x 2 = $1.26), but three stamps will cause you to pay more ($0.63 x 3 = $1.89). If an overpayment is not an issue for you, consider three domestic Forever stamps as an alternative to Global Forever stamps.

United States to Canada

Use Global Forever stamps to send letters from the U.S. to Canada. Each stamp can cover up to 2oz of your mail. If your letter weighs over 2oz, you must purchase additional stamps to cover the postage price.

United States to the United Kingdom

You can use Global Forever stamps to ship mail from the U.S. to the United Kingdom (U.K.). If you have domestic Forever stamps, you can use them as long as they add up to $1.45, the price of one Global Forever stamp.

Coronavirus (COVID-19) Status: Delivering Normally

USPS may require more time to deliver packages and products due to limited transportation availability caused by the COVID-19 pandemic.

Products like Priority Mail and First-Class packages may also temporarily require more time for delivery due to this limited availability.

A Better Way to Manage Shipping Costs

Some people may find it confusing to determine the exact number of stamps to use, especially when figuring out the actual postage cost. USPS has a stamp cost guide to calculate postage manually and a postage calculator to determine the cheapest stamp combination for letters or packages.

Third-party mailing services can also offer competitive postage rates on the market and help organize your mail. Some of these mailing services can also conveniently provide prestamped envelopes and postcards.

The Modern Way of Managing Your Mail

Virtual mailboxes are one way of using technology to manage your mail. You can think of virtual mailboxes as similar to the physical mailbox at your home but with an added layer of security and privacy.

A virtual mailbox lets you view mail that comes to the mailing provider’s secure processing facility and is sent to a virtual address. You can set up your account, and the provider automatically scans your mail items. This way, you only have to view and manage the mail scanned into your account.

This mailbox lets you sort, save, or share mail in PDF (portable document format) to organize your incoming mail easily. Virtual mailboxes can be a helpful alternative to sending and receiving mail, especially if postal workers have difficulty delivering mail to your address.


  1. Postage Stamps
  2. First-Class Mail
  3. Price List
  4. How to Send a Letter or Postcard: Domestic
  5. U.S. Postal Service Announces New Prices for 2023
  6. Delivering for America
  7. Mail & Shipping Services
  8. 2022 Stamp Yearbook
  9. What is the USPS Mail Recovery Center?
  10. How to Send a Letter or Postcard: Domestic
  11. International Stamps
  12. USPS® Coronavirus Updates: Expected Delivery Changes