How many stamps do I need for each ounce?

When sending mail through the United States Postal Service (USPS), knowing how many stamps to use can be confusing. The number of stamps needed depends on the weight and size of the mail piece, as well as the class of mail service being used. This article provides a comprehensive guide on how to determine the correct number of stamps for your mail.

What Are Ounces?

An ounce is a unit of measurement used to determine the weight of an object. There are 16 ounces in one pound. For example, a 5 ounce package weighs 5/16ths of a pound. Ounces are commonly abbreviated as oz.

When sending mail with the USPS, ounces help determine the postage cost. USPS mail is priced based on weight increments, with each additional ounce adding to the cost. Understanding ounces allows you to calculate the exact postage needed for any piece of mail.

How Much Does a Stamp Cost?

The current cost of a First Class Mail Forever stamp is $0.60. This standard stamp can be used to mail letters up to 1 ounce in weight. Heavier letters will require additional postage. Stamps marked with a price instead of “Forever” have a set cash value and can only be used for that priced amount.

Postage Rates By Ounce

Below are the current USPS postage rates for 2023 based on weight increments in ounces:

Weight Postage Cost
0 – 1 ounce $0.60 (1 stamp)
Over 1 – 2 ounces $0.60 + $0.25 per additional ounce
Over 2 – 3 ounces $0.85 + $0.25 per additional ounce
Over 3 – 3.5 ounces $1.10 + $0.25 per additional ounce
Over 3.5 – 4 ounces $1.35 + $0.25 per additional ounce
Over 4 – 5 ounces $1.60 + $0.25 per additional ounce
Over 5 – 6 ounces $1.85 + $0.25 per additional ounce
Over 6 – 7 ounces $2.10 + $0.25 per additional ounce
Over 7 – 8 ounces $2.35 + $0.25 per additional ounce
Over 8 – 9 ounces $2.60 + $0.25 per additional ounce
Over 9 – 10 ounces $2.85 + $0.25 per additional ounce
Over 10 – 11 ounces $3.10 + $0.25 per additional ounce
Over 11 – 12 ounces $3.35 + $0.25 per additional ounce
Over 12 – 13 ounces $3.60 + $0.25 per additional ounce

As shown in the table, 1 stamp covers up to 1 ounce. After that, each additional ounce costs $0.25 extra. So a 2 ounce letter would need $0.60 for the first ounce + $0.25 for the second ounce, totaling $0.85 in postage.

Calculating Stamps Based on Ounces

Figuring out the number of stamps requires simple math:

  1. Weigh your mail piece and determine the ounces.
  2. Check the postage rate table to find the cost for that ounce weight.
  3. Divide the total postage cost by $0.60 (the Forever Stamp value).
  4. Round up to the nearest whole number. This gives you the stamps needed.

For example, say your letter weighs 1.6 ounces. Looking at the table:

  • 1.6 ounces falls in the over 1 – 2 ounce range.
  • The postage for this range is $0.60 for the first ounce + $0.25 per additional ounce.
  • So 1 ounce is $0.60, plus the additional 0.6 ounces at $0.25 each is $0.15.
  • $0.60 + $0.15 = $0.75 total postage.
  • $0.75 divided by $0.60 per stamp equals 1.25 stamps.
  • Rounding up, you would need 2 stamps for a 1.6 ounce letter.

Using this step-by-step calculation will ensure you apply the exact postage required by weight and avoid wasting stamps or having mail returned for insufficient postage.

Non-Standard Shapes and Sizes

The standard letter size that can be sent with regular Forever Stamps is up to 11.5 inches long, 6.125 inches high, and 0.25 inches thick. If your mail piece exceeds these dimensions, extra postage may be required.

Some common non-standard sizes that require additional postage include:

  • Large envelopes (flats) – Starting at $1.00
  • Parcels and packages – Starting at $3.19
  • Square, triangular, or circular shaped mail
  • Normal envelopes over 1/4″ thickness

Use a postal scale at the Post Office to weigh abnormal shapes or oversized envelopes and determine the accurate postage rate.

Using Stamps on Packages and Large Envelopes

Forever Stamps and other regular stamps can be used on large envelopes and packages. However, it typically takes many more stamps to cover the higher postage costs. Determining how many can be inconvenient.

There are a couple options to make paying postage easier for parcels and large envelopes:

  • Purchase a Postal Service postage roll online at You can print the exact amount needed right on the package.
  • Use USPS Click-N-Ship to print shipping labels with the precise calculated rate.
  • Take the package to the Post Office and have the clerk determine the rate and help you pay with a combination of stamps, meter strip, or other postage.

Using one of these methods saves you from having to cover a large package in many small stamps!

Mailing to International Destinations

Standard U.S. postage stamps can only be used to mail items domestically within the United States. To send mail to another country, you must use additional postage to cover the international rates.

Postage for international mail is based on the destination country and the size and weight of the item. Regular Forever Stamps will not be sufficient. At the Post Office, let the clerk know you are sending mail internationally and they can guide you on the proper postage payment.

There are some Forever Stamps designated specifically for international mail. These have markings such as “Global Forever” on them. These stamps can be used in combination with regular ones to make up the total postage for international envelopes or packages.

Additional Postage Options

Besides traditional stamps, there are other ways to pay postage for your mail:

  • Postal Meters – Digital postage printers allow printing exact postage directly on envelopes or labels.
  • Prepaid Envelopes – Such as USPS Priority Mail envelopes with postage included.
  • Online Postage – Services like let you print postage from your home computer.
  • Postage Labels – Self-adhesive labels with printed postage values.
  • Postage Stamps App – Use the USPS app to order and print stamps from your mobile device.

These alternatives can be convenient for bulk mailings, avoiding trips to the Post Office, and paying exact postal fees easily.

Checking USPS Postage Rates Online

The United States Postal Service website provides a handy tool called the Postage Price Calculator. Here you can simply input information like mail type, origin and destination zip codes, date of mailing, and package size and weight.

It will instantly calculate and display the total postage cost. This is the easiest way to find the current rate for any mail or package without having to refer to rate charts.

The calculator includes costs for domestic U.S. mail services like First Class, Priority Mail Express, Retail Ground, Media Mail, and Parcel Select Ground.

It also incorporates international mail classes like First Class Mail International, Priority Mail International, and more. Just choose your destination country to see the right rates.

The Postage Price Calculator removes all guesswork and does the math for you. It’s a quick and convenient online resource.

Understanding Ounce Rates for Stamps

Knowing USPS postage prices by ounce increment ensures proper payment when using stamps. An envelope’s weight dictates the number of stamps required.

One Forever Stamp covers 1 ounce. Additional ounces add $0.25 per ounce to the cost. Simply weigh your mail piece, check the rate table, calculate the total postage, and divide by $0.60 per stamp to determine how many you need.

Non-standard mail may require extra postage beyond typical ounces rates. Use online calculators or the Post Office for guidance when mailing irregular shapes and sizes.

Following ounce rate guidelines guarantees accurate postage payment and smooth delivery of your letters and packages.


Determining how many stamps to use for mail can seem complicated, but understanding ounces and USPS postage rates simplifies the process. Weighing your envelope or package tells you the ounce increment to check the rate table and calculate the total postage cost. From there, just divide by the $0.60 value of a Forever Stamp to see how many stamps are needed per ounce of mail.

Following this easy step-by-step guidance, using online resources like the USPS Postage Price Calculator, and asking Post Office clerks when unsure makes paying for postage a breeze. Now you can mail letters and parcels with confidence knowing exactly how many stamps to use based on weight in ounces.

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