How do you know if a letter needs 2 stamps?

Quick Answer

The basic rules for determining if a letter needs additional postage beyond a single First Class Mail stamp are:

  • If the letter weighs more than 1 ounce, it needs additional stamps. Each additional ounce over 1 ounce requires an extra First Class Mail stamp.
  • Non-machinable letters that are rigid, uneven, or thicker than a quarter inch also require extra postage beyond a single stamp.
  • The shape and dimensions of the letter can affect the postage required. Large envelopes and oddly shaped mail may cost more.
  • International mail often requires extra postage. Letters sent to other countries frequently need more than a single First Class Mail stamp.

Knowing the weight, dimensions, and destination of your mail piece are key factors in figuring out if more than one stamp is needed. The standard cost for a 1 ounce domestic letter with a standard envelope shape is the value of one First Class Mail stamp. Exceeding size limits, weight limits, thickness limits, or sending mail abroad can all increase the postage required.

Weighing Your Letter

The most straightforward way to determine if a letter needs extra postage is to weigh it. The current price of a 1 ounce First Class Mail stamp covers a 1 ounce letter. If the letter weighs more than 1 ounce, each additional ounce requires one extra stamp.

For example, if a letter weighs 1.5 ounces, it would need two Forever stamps or the equivalent postage. One stamp covers the first ounce, while the extra half ounce requires a second stamp.

To weigh a letter accurately at home, you can use a small digital scale. These are inexpensive and widely available. Scales designed specifically for weighing mail and packages will provide weight measurements in ounces.

Once the total weight of the letter is known, determining the stamps required is simple math:

  • 1 ounce or less = 1 stamp
  • Over 1 ounce to 2 ounces = 2 stamps
  • Over 2 ounces to 3 ounces = 3 stamps

And so on, adding one additional stamp for each extra ounce over the first. When you bring mail to the post office, the retail counter can also weigh it for you if you do not have an accurate scale at home.

Heavier letters with lots of pages or enclosures will weigh more and cross over the 1 ounce threshold quickly. Even a few sheets of paper can add enough weight to tip the scales over an ounce. Knowing the complete weight is a foolproof method for figuring out if extra postage is owed.

Checking Letter Dimensions

The size and shape of a mail piece can also impact the required postage. Letters that are unusually large, rigid, or uneven may incur surcharges or require extra stamps.

The United States Postal Service defines a standard letter-sized envelope as having these maximum dimensions:

  • Height: 6 1/8 inches
  • Length: 11 1/2 inches
  • Thickness: 1/4 inch

Envelopes exceeding these dimensions may be subject to non-machinable surcharges. This includes letters that are too rigid, uneven, or thick to run efficiently through postal equipment. Some examples of non-machinable letters include:

  • Oversized envelopes
  • Boxes, tubes, or cylinders
  • Bumpy or lumpy mail
  • Envelopes with rigid objects inside
  • Letters thicker than 1/4 inch

To remedy non-machinable surcharges, extra postage can be added to the letter. Typically this means adding an extra ounce rate beyond the weight-based stamps.

For instance, a large but lightweight greeting card may only weigh half an ounce. But the size makes it non-machinable. So extra postage would be needed on top of the half-ounce stamp to bring it up to the full 1 ounce rate.

Checking that your mail piece falls within standard size guidelines can help avoid extra postage charges. If the dimensions exceed maximums, extra stamps may be required regardless of weight.

Mailing to International Destinations

Sending letters and packages abroad also often necessitates additional postage beyond simple domestic rates. Each country has its own fees for inbound international mail. Let’s look at some examples:

Destination Postage Rate from U.S.
Canada Global Forever Stamp
Mexico Global Forever Stamp
United Kingdom Global Forever Stamp

As seen in the table, letters under 1 ounce sent to Canada, Mexico, and the United Kingdom all require just a single Global Forever Stamp. This special stamp is valid for sending 1 ounce letters abroad, but it costs slightly more than a domestic stamp.

However, many other countries have higher fees that will necessitate extra postage:

Destination Postage Rate from U.S.
China $1.30
India $1.20
Saudi Arabia $1.30
France $1.40

As shown, popular destinations like China, India, Saudi Arabia, and France all charge at least $1.30 and up for a basic 1 ounce letter. To cover this higher international rate, additional stamps would need to be added to reach the total cost.

Depending on the destination country, sending letters abroad may require planning for extra postage costs. Checking the postal rate charts on for the nation you are mailing to can provide guidance on the stamps needed.

Some letters, like postcards, may have separate international pricing as well. But in most cases an extra stamp or two does the trick to reach the required fees. Leaving letters underpaid when sending to another country can cause significant delays or rejection of the mail.

When Extra Ounces Are Free

In some situations, adding extra weight to a letter does not actually change the postage rate. These cases include:

  • Forever Stamps – The forever stamp type always covers a basic 1 ounce letter, regardless of weight fluctuations.
  • Precanceled Stamps – Rate is set for specific services like Priority or Express Mail.
  • Metered Mail – Printed label rate applies up to 1 ounce. Extra weight is free.

Because of these exceptions, weighing the mail may show it is over 1 ounce but no extra stamps are needed. This is contingent on using Forever, precanceled, metered, or other applicable stamps.

However, size and machinability factors can still necessitate additional postage even when extra weight is permitted. Non-standard envelopes or rigid objects may lead to surcharges with the above stamp types, despite the free extra ounce allowance.

Checking Current Postage Rates

The cost to mail letters and packages can change over time as USPS adjusts their pricing. To be sure you have accurate rate information, checking current published postage prices is advisable.

The Postal Service provides tools to look up the exact rates in effect today for different mail classes and services. Options to find current pricing include:

  • USPS Postage Price Calculator – Online calculator with dropdown menus.
  • Price Lists – Downloadable PDF files listing prices.
  • Quick Tools – Pricing for common mailpieces like letters, postcards, boxes.
  • Retailcounter – In-person assistance at the Post Office.

Rates for domestic and international letters and packages are updated each year or more frequently. Changes typically go into effect on January 1 for the new year.

Consulting the most up-to-date postage charts and calculators ensures you are not underpaying due to outdated rate information. This helps avoid mail being returned or delayed due to insufficient stamps.

Proper postage is required for the weight, size, and destination according to current rates. Checking USPS pricing tools can prevent guessing about whether additional stamps are needed.

Automation and Forever Rates

One nuance to be aware of when checking postage prices is the difference between “automation” and “non-automation” rates.

  • Automation rates apply to machine-readable letters with typed addresses and standard envelope shapes.
  • Non-automation rates are higher and apply to mailpieces that must be sorted manually by postal workers.

The forever stamp is equal to the automation rate for a 1 ounce letter. So forever stamps purchased in a previous year when rates were lower may now underpay non-automated letters at today’s prices.

The non-automated additional ounce rate can be 10 cents or more higher than the automated rate. So checking current pricing provides guidance on how many extra stamps are necessary on oddly-shaped envelopes and handwritten mail.

Using Postage Stamps as Needed

Understanding the factors that can increase postage requirements allows you to accurately apply the needed stamps. A kitchen scale, tape measure, and USPS rate charts help identify when extra stamps should be used.

Some tips for getting full postage on letters include:

  • Weighing letters over 1 ounce and adding the right additional stamps.
  • Checking dimensions against size restrictions.
  • Adding extra postage for non-machinable shape and thickness.
  • Looking up current international rates if mailing abroad.
  • Using enough additional stamps to bring postage up to required prices.

Applying adequate postage prevents delays from insufficient payment. Letters may be returned if stamps do not fully cover weight, size, machinability, or destination requirements according to the latest USPS rates.

Carefully checking factors like weight, dimensions, and destination before mailing can ensure your letters and packages have the required postage.


Determining if extra postage stamps are needed beyond a single Forever stamp can be done by:

  • Weighing the letter to check if it exceeds 1 ounce.
  • Measuring dimensions to see if it is oversized or non-machinable.
  • Reviewing destination to see if international postage applies.
  • Consulting current USPS price listings for accuracy.
  • Adding additional stamps according to weight, size, and destination.

Using scales, rulers, and USPS resources allows you to properly calculate postage. Applying enough stamps prevents delivery delays or return of insufficiently paid mail. Forever stamps cover 1 ounce domestic letters, but anything heavier, bulkier, or international will likely need extra postage. Checking factors like weight, shape, and destination confirms if more than a single stamp is required.

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