Yes, you can use US stamps for international mail, as long as the total face value on the envelope meets the international rate. For a one-ounce letter or postcard to any country, that rate is $1.70, which is exactly what a single Global Forever stamp covers.1USPS. How to Send a Letter or Postcard: International One regular domestic Forever stamp on its own is not enough, so you either add more stamps to reach $1.70 or use a Global Forever.
Making Domestic Stamps Add Up to the International Rate
The USPS does not require a specific type of stamp for international letters. Any combination that reaches the correct postage works: domestic Forever stamps, older commemoratives from a drawer, or small denominations like 1¢, 2¢, 3¢, 5¢, and 10¢ stamps sold at the Postal Store.1USPS. How to Send a Letter or Postcard: International
The awkward part is the arithmetic. A domestic Forever stamp’s value does not divide evenly into $1.70, so combinations built from Forevers alone usually overpay by a few cents. That is fine. The USPS accepts extra postage; it just will not accept short postage. If you send letters abroad regularly, a Global Forever stamp is the cleaner tool because it is designed to cover exactly one ounce of international First-Class letter mail and keeps its value even after the rate rises. For a one-time letter with stamps already on hand, stack enough of them to clear $1.70 and drop it in.
Small-denomination stamps are the practical fix when your leftover stamps land just under the rate. Adding a 10¢ and a 5¢ to a mix of Forevers, for instance, gets you cleanly over the line without wallpapering the envelope.
What Happens If the Postage Is Short
Mail with insufficient postage is returned to the sender.2USPS. Return to Sender Mail Rounding down is not an option, and the risk gets higher if the envelope is heavier than you think, oddly shaped, or rigid. If you are not sure, take it to a post office counter and have the clerk weigh it and confirm the postage before it goes out.
The Rate You Are Trying to Hit
For most people asking this question, the target is $1.70: a standard one-ounce letter or postcard to any country under First-Class Mail International, which reaches more than 180 destinations.3USPS. First-Class Mail International A single Global Forever stamp covers it, and the stamp remains valid at that use even if the price later changes. The next USPS price adjustment is scheduled for July 12, 2026.4USPS. International Mail Services and Shipping Rates
A few size and shape rules affect whether $1.70 is actually enough:
- Standard letters must be no longer than 11½ inches, no taller than 6⅛ inches, and no thicker than ¼ inch.5Postal Explorer. 240 First-Class Mail International
- Letters that are square, rigid, or unusually shaped carry a nonmachinable surcharge of $0.49 on top of the regular postage. A square greeting-card envelope is the common trigger.6USPS. First-Class Mail International Letters 2026 Pricing Data
- Large envelopes (flats) can weigh up to 15.994 ounces, with prices starting at $3.15 and rising with weight and destination.7USPS. Mailing and Shipping Prices – Section: International Prices
Anything heavier or bulkier than a letter, and certainly anything containing merchandise, moves into package services with their own pricing, and stamps stop being the practical way to pay. For those, the USPS price calculator at usps.com gives the current rate for the specific item.4USPS. International Mail Services and Shipping Rates
Addressing Rules That Trip Up International Letters
Correct postage is only half the job. Incorrect addressing is one of the easiest ways to get international mail delayed or lost, and the format differs from what you would use domestically. Write the full delivery address in capital letters using the Roman alphabet and Arabic numerals, keep it to five lines or fewer, and put the city and postal code together in capitals. The last line of the address must contain only the full country name, spelled out completely in capital letters with no abbreviations.8Postal Explorer. Addressing Writing “UK” instead of “UNITED KINGDOM,” or “UAE” instead of “UNITED ARAB EMIRATES,” can cause processing errors.
If the recipient’s address is written in a non-Roman script such as Arabic, Chinese, Japanese, Russian, or Greek, include an English translation of the full name and address between the lines. When you do not know the translation, transliterate the foreign characters into Roman letters.8Postal Explorer. Addressing
Do You Need a Customs Form?
For a stamped letter, usually no. A First-Class Mail International letter or large envelope that weighs under 15.994 ounces and contains only documents or personal correspondence needs no customs form.9USPS. Customs Forms Everything else headed to another country does, including any package, anything containing merchandise or goods, and mail to US embassies or military bases overseas. If you are slipping a small item into the envelope rather than a card or letter, you have crossed into customs-form territory, and handwritten forms are no longer accepted; they must be generated electronically through Click-N-Ship or at the counter.10Postal Explorer. Customs Forms and Online Shipping Labels
Check Whether Service Is Suspended to Your Destination
Postage does not help if the USPS is not currently delivering to the country. As of March 2026, all international mail services are suspended to Afghanistan, Armenia, Bahrain, Belarus, Bhutan, Cuba, Eritrea, Haiti, Iran, Iraq, Israel, Kuwait, Pakistan, Qatar, Russia, Seychelles, South Sudan, Sudan, Syria, Turkmenistan, United Arab Emirates, Venezuela, and Yemen.11USPS About. International Mail Service Suspensions The list changes with conditions, so check the USPS service alerts page before mailing to a destination you are unsure about.
Where to Get the Stamps
Global Forever stamps and other international postage are sold at any local post office. The USPS Postal Store at store.usps.com carries Global Forever stamps and the smaller denominations useful for building up to the right amount when you are working with what is already on hand.12USPS. The Postal Store – Stamps, Mailing Supplies and Collectibles Some large retail chains also stock Global Forever stamps.