Postage Weight


March 23, 2024

The Hope Diamond is the biggest-known deep blue crystal in the world. Today, it would have a staggering value of around $200 to $300 million.

One might assume that such a priceless and revered treasure would demand the utmost security, safeguarded behind layers of impenetrable vaults and guarded by an army of security personnel.

But in an intriguing twist, the renowned jeweler Harry Winston defied expectations in 1958. He mailed the precious stone through the U.S. Postal Service (USPS). And the postage cost of this daring expedition? A mere $2.44.

While the Hope Diamond was valuable, it only weighed 45.52 carats, a fraction of an ounce. This astonishing tale in postal history highlights one of the primary elements influencing shipping rates- a mailpiece’s weight.

This article breaks down postage weight, from how it affects mailing prices to the limits of the various USPS services. 

Do you want to know how much sending a specific item will cost? Visit your local post office. Use’s USPS facility finder tool to find your area’s nearest one.

How Much Is It to Mail a Letter?

One common question mailers have is, “How much does it cost to mail a letter?” The answer to this question depends on various factors, including the letter’s size, shape, and weight.

It’s a good thing the United States Postal Service (USPS) supplies a simplified solution to determining letter postage costs – the USPS First-Class Mail service.

Calculating the shipping rate for First-Class Mail letters is straightforward. If your mailpiece is within USPS’ standard letter dimensions, you’ll only pay $0.66 for the first ounce. You’ll then pay $0.24 for each additional ounce up to 3.5oz.

Note that a standard-sized letter is at least 5” long and 3½” tall and isn’t more than 11½” in length, 6 ⅛” in height, and ¼” in thickness. 

If your item exceeds these size limits, USPS will consider it a large envelope or flat and will charge it as such.

Weighing Your Mail to Figure Out Postage

Sending letters and postcards via the Postal Service is economical. However, they aren’t the only mail items you can ship with USPS. Unfortunately, the same principle applies: a parcel’s weight and size significantly influence the shipping cost.

Postage fees can get expensive, especially if you frequently mail larger, hefty pieces. So, you must determine your shipment’s weight accurately. Fortunately, this process is relatively foolproof and can be done in the comfort of your home.

Why Weigh Mail at Home?

One of the most significant benefits of weighing your mailpieces at home is convenience. While there are over 31,000 post office locations nationwide, visiting one can be time-consuming, especially in high-foot-traffic areas.

Conducting the weighing process eliminates the guesswork, allowing you to get your mailpiece’s weight and measurements accurately. In doing so, you determine the appropriate service to use and the amount of postage, resulting in cost savings.

Calculating Postage

As mentioned, postage rates are generally based on the parcel’s size, shape, and weight. However, some USPS mailing options also consider the destination, speed, and add-on services into this equation, which can complicate things.

For instance, USPS Ground Advantage pricing includes the zone or distance an item will travel. The two- to five-business-day shipping for a package weighing 20oz to a location 100 miles away (Zone 2) will cost $18.40.

Fortunately, you can streamline how to calculate postage using the U.S. Postal Service’s postage price calculator tool, choosing the “calculate price based on shape on size” option and providing your parcel’s weight

Weigh Your Mail and Round-Up

Here’s a tidbit you may not know: USPS rounds up a mailpiece’s weight by the next pound or ounce. In other words, if your parcel weighs 3.5lbs, the Postal Service will charge you the 4lb rate.

Therefore, you must also round up when weighing your shipments. Otherwise, you may calculate the incorrect postage amount needed, resulting in delivery delays or returns.

Select a Mail Class

As mentioned, weighing your mailpieces allows you to determine which USPS service to choose, as each has weight limits. 

For example, First-Class Mail items can be at most 13oz, while Priority Mail parcels can reach up to 70lbs.

How to Weigh Mail at Home

There are various ways you can weigh your shipments at home. Using a scale will be your best bet for getting an accurate reading. As such, consider investing in a postal scale, which you can purchase from the USPS store, post office, or local office supply retailer.

Best Scale for Weighing Mail

Not all scales are created equal. Some will do better than others. For instance, the Reshy scale can weigh with an accuracy of 0.004oz.

On the other hand, a SurmountWay scale has a minimum weighing capacity of 0.7lbs, which won’t even register the Hope Diamond.

Ultimately, the best scale is what you have on hand. Fortunately, you can always seek help from Postal Service representatives at your local post office. Visit to find your area’s most convenient USPS facilities quickly.


Pricing between delivery options can vary wildly. Although a mailpiece’s weight can significantly drive the shipping cost, the USPS mailing service you use to ship can do the same. 

Let’s explore the postal rates of domestic and international USPS mail and package shipping services.

Domestic Prices

Here are the retail and commercial starting prices of the U.S. Postal Service’s domestic mailing options, based on October 2023 data:

ServicePost Office PriceCommercial Price
Priority Mail Express$28.75$24.90
Priority Mail Express Flat-Rate Envelope$28.75$24.90
Priority Mail Express Return$24.90
Priority Mail$9.35$7.64
Priority Mail Flat Rate Envelope$9.65$8.05
Priority Mail Return$7.65
First-Class Mail$0.66$0.49
USPS Ground Advantage$4.75$3.59
USPS Ground Advantage Return$4.75$3.59
USPS Marketing Mail$0.19
Parcel Select$3.78
Parcel Select Lightweight$2.46
Media Mail$3.92$2.59
Library Mail$3.72$2.46

Domestic Letter Mailing – Price per Ounce

The postage rate for First-Class domestic letter mailing starts at $0.66 for the first ounce. You’ll pay an additional $0.24 for each subsequent ounce up to 3.5oz. 

In other words, expect to pay as low as $0.66 and as much as $1.38 to send a domestic letter.

Domestic Envelope Requirements and Costs

USPS will charge large envelope rates if your letter exceeds First-Class Mail’s standard size. However, large envelopes or flats have specific size and weight restrictions.

The maximum dimensions for large envelopes are 15” long, 12” tall, and ¾” thick. Conversely, the weight limit for flats is 13oz. 

Now, for the cost. Here’s an overview of First-Class Mail large envelopes’ retail rates as of October 2023:


Domestic Postcard Shipping

Like other mailing items, postcards follow specific size restrictions. An item must be at least 5” long and 3½” tall to qualify as a postcard. However, it cannot exceed dimensions of 6” in length, 4¼” in height, and 0.016” in thickness.

Fortunately, the pricing structure for postcards is straightforward. To ship one via the U.S. Postal Service’s First-Class Mail option, you’ll pay $0.51.

International Prices

Despite its primary purpose of serving the American people, the United States Postal Service handles 44% of the world’s mail. USPS does this through its reliable and reasonably priced international shipping services.

Here’s a quick look at the starting USPS postage rates for its international mail and package delivery options based on October 2023 information:

ServicePost Office PriceCommercial Base Price
Global Express Guaranteed$71.10$67.55
Priority Mail Express International$56.00$53.07
Priority Mail Express International Flat-Rate$54.75$51.98
Priority Mail International$42.10$39.53
Priority Mail International Flat-Rate Envelope$30.35$28.57
Priority Mail International Small Flat-Rate Box$31.45$29.64
Priority Mail International Medium Flat-Rate Box$60.55$56.10
Priority Mail International LargeFlat-Rate Box$74.00$69.10
First-Class Mail International$1.50(Letters and postcards for all countries$3.00(Large Envelopes for all countries)
First-Class Package International Service$15.75$14.96
Airmail M-Bag$55.00$30.00 (International Priority Airmail M-Bag)
$30.00 (International Surface Air Lift M-Bag)
International Business Reply Service$2.10

International Shipping Letter Postage

The pricing structure for international letters is similar to that of domestic ones. The only difference is that First-Class Mail International considers the destination country, which it divides into price groups.

Country price groups refer to the postage rates the USPS assigns each country. This system allows the government agency to quickly determine the shipping costs for international shipments.

Here’s how these postage costs look as of October 2023:

WeightCanadaMexicoPrice Group (3 to 5)Price Group (6 to 9)

New Stamp Rates

USPS updates its stamp rates periodically. The most recent update occurred on July 9, 2023, involving a price increase on First-Class Mail stamps. This change raised the stamp cost from $0.63 to $0.66.

The recent rate modification also affected the following products:

ProductPrevious PricesNew Prices
Domestic postcard stamps$0.48$0.51
International postcard stamps$1.45$1.50
International 1oz letter stamps$1.45$1.50

For up-to-date information on postal rates, visit the USPS website at 

Alternatively, you can talk to a USPS retail associate at your local post office. Use’s post office finder to find your area’s nearest one.

Domestic Priority Mail Flat Rates

One of the reasons why many consider the U.S. Postal Service an affordable courier service is its Priority Mail flat-rate options. At their core, these envelopes and boxes let you ship items up to 70lbs to any domestic address for the same price.

Here’s the October 2023 retail and commercial pricing for Priority Mail flat-rate products:

ProductPost Office PriceCommercial Price
Flat Rate Envelope$9.65$8.05
Window Flat Rate Envelope$9.65$8.05
Small Flat Rate Envelope$9.65$8.05
Padded Flat Rate Envelope$10.40$8.80
Legal Flat Rate Envelope$9.95$8.35
Small Flat Rate Box$10.20$8.55
Medium Flat Rate Box (top-loading)$17.10$14.75
Medium Flat Rate Box (side-loading)$17.10$14.75
Large Flat Rate Box$22.80$19.90
APO/FPO/DPO Flat Rate Box$21.20$18.35
Large Flat Rate Board Game Box$22.80$19.90
Prepaid Forever Priority Mail Flate Rate Packaging$9.65

Additional Services Rates

The U.S. Postal Service offers optional services to improve the reliability and security of your shipments. These add-ons include return receipts, certificates of mailing, and insurance. 

Here’s a look at the October 2023 additional service rates:

Add-On ServicePrice
Certified Mail$4.35
Certificate of Mailing$1.95
Return Receipt$3.55 (Hard copy)$2.20 (Electronic)
Insured MailStarts at $2.70
Registered MailStarts at $16.80

Weight, Size, and Shape Requirements

USPS has strict guidelines for mailpieces’ weight, size, and shape. Understanding these requirements is crucial in ensuring you can ship your mail via your desired service.

Additional Charges for Irregular Mailpieces, Envelopes, and Small Packages

The U.S. Postal Service considers the mail’s shape when determining the shipping cost. Parcels that aren’t uniformly thick, irregularly shaped, or too rigid incur additional fees, regardless of the postage weight.

Nonmachinable Envelopes

USPS uses automated machines to process and sort envelopes. A postal worker must manually cancel an envelope that doesn’t fit USPS’ shape standards and cannot go through the postal machines. 

In these scenarios, USPS will charge a nonmachinable surcharge. This penalty costs $0.40.

Large Mailpieces, Envelopes, and Small Packages

As mentioned, Postal Service delivery options have size requirements and guidelines. If your mailpiece fails to meet these conditions, USPS may require you to pay the shipping rates of the following mail class.

For instance, First-Class Mail large envelopes that surpass 15” long, 12” tall, and ¾” thick will be charged package prices and will be sent via USPS Ground Advantage. Depending on the item’s weight and destination, shipping can cost you between $4.75 and $233.75.

First-Class Mail

When discussing USPS services and postage weights, you must include First-Class Mail. According to the U.S. Postal Service, First-Class Mail is its most cost-efficient service weight-wise for sending letters, postcards, and large envelopes.

Mail in 1–5 Business Days; Small Packages in 1–5 Business Days

First-Class Mail boasts a reasonable delivery time of one to five business days. While it isn’t the Postal Service’s fastest mail and package delivery option, what it lacks in speed, it makes up for in affordability.

Features and Pricing

First-Class Mail caters to domestic and international mailpieces. First-Class Mail International service allows you to ship to over 180 countries, including Australia, Canada, and Great Britain.

Like its domestic counterpart, First-Class Mail International is an affordable mailing solution for items with a postage weight of up to 15.994oz – less than a pound.

Global Forever® (International)

As previously mentioned, First-Class Mail International has a relatively straightforward pricing structure based on weight and country price group. However, the U.S. Postal Service simplifies calculating postage costs further with its Global Forever stamp system.

Global Forever stamps are postage stamps that are always equal to the cost of mailing a 1oz letter via First-Class Mail International, which is, as of October 2023, $1.50. In other words, you only need to buy one Global Forever stamp for every 1oz-letter.


USPS’ domestic First-Class Mail service only allows you to ship mail weighing up to 13oz with restrictions on dimensions. Otherwise, USPS will charge you parcel rates.

 On the other hand, First-Class Package International allows you to ship items with a combined length, height, and depth of 36”. It also lets you send mailpieces with a postage weight of up to 64oz or 4lbs.

While First-Class Package International rates consider the destination country’s price group, it’s one of the U.S. Postal Service’s economical international shipping solutions, with prices starting at $15.75.

The Easiest Way to Know How Many Stamps You’ll Need

USPS’ Click-N-Ship is a tool that lets you print labels online and pay postage for Priority Mail, Priority Mail Express, and Ground Advantage packages online. However, you’ll use traditional postage stamps when using First-Class Mail for your shipping needs.

Determining the appropriate number of stamps to cover your mailpiece’s postage cost can sometimes be overwhelming, especially considering various types of stamps exist.

The most effortless workaround for this dilemma is to contact USPS through its customer service hotline at 1-800-ASK-USPS (1-800-275-8777) or your local post office. Visit to find your area’s most convenient post office locations.

How Many Stamps per Ounce Are Needed for First-Class Mail?

The number of stamps you need to cover the cost of shipping a First-Class Mail item depends on the weight. Fortunately, the U.S. Postal Service has specialty stamps explicitly designed for every First-Class Mail scenario.

3.5 Ounces Is the Maximum for How Heavy a First-Class Letter Can Be

As mentioned, the maximum weight for a First-Class Mail letter is 3.5oz. USPS’ First-Class stamps cover the 1oz postage cost. 

On the other hand, Additional Ounce stamps cover the price of subsequent ounces, which is, as of October 2023, $0.24.

To cover the $1.38 shipping cost of mailing the 3.5oz maximum weight of a First-Class Mail letter, you need one First-Class stamp plus three Additional Ounce stamps ($0.66 + [$0.24 x 3] = $1.38).

How Many Stamps Do I Need for a Large Envelope?

The number of stamps you need can vary depending on your large envelope’s weight. Let’s assume that your flat weighs 5oz. In this scenario, you need enough postage stamps to cover $2.31.

A possible combination of stamps is three First-Class stamps, an Additional Ounce stamp, and a denominated stamp worth $0.09 ([$0.66 x 3] + $0.24 + $0.09 = $2.31).

How Many Stamps Will I Need to Send a Domestic Package?

Calculating postage and the appropriate number of stamps to cover that price involves some mathematics. Fortunately, there are ways you can avoid calculation errors.

  1. Calculating Postage at the Post Office

As mentioned, it’s best to seek help from Postal Service representatives at your local post office. These professionals will assist you in calculating the postage cost based on your package’s weight, size, and destination.

  1. Using a Postage Calculator

If you don’t have the time or simply want to avoid the hassle of visiting a USPS facility, you can use a postage calculator. Visit the USPS website at for details.

Where to Buy the Stamps You Need and the Postage Costs

Postage stamps are vital in covering the postage cost of mailing an item. Fortunately, locating a place to buy them won’t ever be a problem, as you have various options.

Your local post office is the first choice. However, if you want the convenience of online shopping, you can purchase stamps from the Postal Store. Alternatively, you can call USPS and order by phone at 1-844-737-7826.

You can also buy postage stamps by mailing or faxing a stamp order form (PS Form 3227-A). Additionally, you have online retailers like Amazon, pharmacies like CVS, and financial institutions as alternatives.

Using Forever Stamps to Cover First-Class Postage

Since the U.S. Postal Service introduced them in 2007, Forever stamps have become a staple for covering First-Class Mail postage. Let’s explore what Forever stamps are and how they work.

What are Forever Stamps?

In a nutshell, Forever stamps are specialty stamps that will always be equal to the postage rate of mailing a 1oz First-Class Mail letter. The most substantial advantage of Forever stamps is that they retain their value even if shipping rates change in the future.

How Do I Use Forever Stamps?

Using Forever stamps is as simple as sticking it to your mailpiece. If you’re sending a 1oz letter via First-Class Mail, affix it to the envelope, and you’ve covered the postage cost.

How Many Forever Stamps per Ounce?

One Forever stamp equals the shipping cost of a 1oz First-Class Mail letter. So, to cover the first ounce, you need one Forever stamp. 

If you’re shipping more than an ounce, you can use Additional Ounce stamps to cover the excess.

Additional Information

In addition to postage weights, rates, and using Forever stamps, there are several other essential details to be aware of when sending mail through the Postal Service.

Let’s discuss what these considerations are.

Mailing Restrictions and Prohibitions

The U.S. Postal Service has strict size, shape, and postage weight guidelines. However, it also determines what you can and cannot ship through its mailing network.

USPS prohibits shipping these items, even if they meet the size and weight policies: airbags, ammunition, explosives, gasoline, liquid mercury, and marijuana. USPS also limits the delivery of hazardous materials (HAZMATs), such as lithium batteries. 

For an exhaustive list of restricted and prohibited items, visit the USPS website at

Alternatively, you can consult a local post office’s retail associate. Use’s USPS facility locator tool to narrow the over 31,000 post office locations nationwide to ones in your area.

For Businesses

If you’re a small business owner or are a representative of a company that requires a high-volume mailing solution that offers speed, security, and affordability, USPS offers services and resources worth considering.

Data-Driven Shipping

One of the Postal Service’s offerings that can help you streamline your mailing needs is data-driven shipping solutions. These options provide targetable, trackable, and measurable services, optimizing your mail delivery processes and reducing costs.

Commercial Prices and Automation Discounts

USPS boasts economical retail prices. However, you can lower your mailing costs with commercial pricing. If you presort and ensure your mail items are automation-compatible, you can bring down the shipping price with USPS further.

Note that commercial base pricing requires a minimum quantity of 500 mailpieces. Additionally, presorted mail refers to those bundled by ZIP code.

At the same time, automation-compatible mailpieces meet the basic standards for First-Class Mail, are sealed, and meet the paper weight guidelines, among other requirements.

For additional information on the U.S. Postal Service’s business mail and package delivery solutions, visit your local post office. Find your nearest USPS facility with


  1. How many stamps do I need per weight?

The number of stamps you need depends on the parcel you want to send. For instance, a postcard requires only one stamp – a Postcard stamp.

However, a large envelope weighing 1oz will cost $1.35 to ship and will require two First-Class stamps and a denominated stamp with a value of $0.03 ([$0.66 x 2] + $0.03 = $1.35).

  1. How many stamps do I need 1.5oz?

One First-Class or Forever stamp covers the $0.66 postage cost of a letter with a weight not over 1oz. For a 1.5oz letter, you must pay the 2oz price of $0.90. In this scenario, you’ll need a Forever stamp and an Additional Ounce stamp ($0.66 + $0.24 = $0.90).

On the other hand, a flat weighing 1.5oz will cost you $1.59 or the 2oz rate because the weight exceeds 1oz. A large envelope weighing 1.5oz will require two Forever stamps, an Additional Ounce stamp, and a denominated stamp worth $0.03 ([$0.66 x 2] + $0. 24 + $0.03 = $1.59).

  1. How many stamps do I need for three ounces?

The cost to send a 3oz letter is $1.14. In this mailing scenario, you’ll need one First-Class Mail stamp plus two Additional Ounce stamps ($0.66 + [$0.24 x 2] = $1.14).

Meanwhile, the shipping rate for a 3oz large envelope is $1.83. To cover the postage, you must use two Forever stamps, two Additional Ounce stamps, and a denominated stamp equal to $0.03 ([$0.66 x 2] + [$0.24 x 2] + $0.03 = $1.83).

  1. What happens if I don’t have the right amount of stamps?

If you don’t have the correct postage, USPS may tag your mailpiece as “Postage Due.” When this happens, the Postal Service will attempt to collect the balance from the recipient.

Unfortunately, USPS may return the parcel if the intended receiver refuses to pay for the missing postage. If the item doesn’t have a return address, the U.S. Postal Service may dispose of it.


  1. Ten Weird Things People Have Shipped with USPS
  2. The Hope Diamond
  3. USPS Price List
  4. First-Class Mail
  5. What Are You Mailing? Domestic
  8. USPS Ground Advantage
  9. USPS Zone Map
  10. Is it Legal to Put Flyers in Mailboxes?
  11. Priority Mail
  12. Mailing & Shipping Prices
  14. How Many Stamps Do I Need?
  15. U.S. Postal Service Files Notice with PRC for New Mailing Services Pricing
  16. First-Class Mail International
  17. Postage Stamps – The Basics
  18. First-Class Package International Service
  19. Print Click-N-Ship Online Postage
  20. Contact USPS
  21. Where to buy postage stamps, including the post office, online, ATMs, and grocery stores
  22. Domestic Shipping Prohibitions, Restrictions, & HAZMAT
  23. Presorting Your Mail
  24. 230 Commercial Mail First-Class Mail
  25. 200 Commercial Letters, Cards, Flats, and Parcels
  26. What Happens if I Didn’t Put Enough Postage?