How Many Forever Stamps Do I Need? Weight, Size and Postage
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One standard domestic Forever stamp covers a qualifying U.S. letter weighing up to 1 ounce. A heavier envelope, a different mail category, or an international destination can require more postage. Count stamps only after you know the price for the finished piece.
USPS rates checked September 6, 2026. The prices below took effect July 12, 2026 and refer to retail postage for mail sent from the United States. They are postage values, not this store's selling prices.
Start with these four checks
- Destination: is this domestic mail or mail to another country?
- Mail category: is it a letter, postcard, large envelope, or package?
- Finished weight: weigh the sealed envelope with everything inside.
- Shape and flexibility: measure the envelope and check for stiffness, lumps, or unusual closures.
Keep a short note with the weight and measurements. That makes the next step easier and gives you something concrete to check if you change the contents. A paper-count estimate is less useful: stationery, envelope liners, and even different paper stocks can change the result.
How many stamps for a standard domestic letter?
The table applies only to qualifying, machinable First-Class Mail letters, without extra services. A standard domestic Forever stamp currently represents $0.82. USPS lists these stamped-letter prices in its current Notice 123 price list.
| Finished weight | Postage needed | If using only standard Forever stamps |
|---|---|---|
| Up to 1 oz | $0.82 | 1 stamp; exact postage |
| Over 1 oz, up to 2 oz | $1.11 | 2 stamps; $0.53 extra |
| Over 2 oz, up to 3 oz | $1.40 | 2 stamps; $0.24 extra |
| Over 3 oz, up to 3.5 oz | $1.69 | 3 stamps; $0.77 extra |
These counts show sufficient postage value, not the least expensive combination. The additional-ounce price is $0.29. For a qualifying 2-ounce letter, one standard Forever stamp plus one Additional Ounce stamp provides $1.11. Two Additional Ounce stamps added to one standard Forever provide $1.40 for the 3-ounce tier.
Notice the last row: two standard Forever stamps total $1.64, which is five cents short of the $1.69 price for a letter over 3 ounces and up to 3.5 ounces. Weighing accurately matters even when the difference seems small.
Check the envelope before using the table
USPS letter limits are 5 to 11½ inches long, 3½ to 6⅛ inches high, and 0.007 to ¼ inch thick, with a maximum weight of 3.5 ounces. To remain machinable, pieces more than 6 inches long or more than 4¼ inches high must be at least 0.009 inch thick. A suitable length-to-height ratio, flexibility, and other conditions also apply.
A square envelope, excessive rigidity, uneven contents, or certain closures can make a letter nonmachinable. The current surcharge is $0.49, so a qualifying nonmachinable letter up to 1 ounce needs $1.31. Paying that surcharge does not turn every thick or rigid item into a letter. Check the USPS physical standards or ask a postal employee to assess the piece.
For invitation suites with decorative details and separate reply envelopes, use our wedding invitation postage checklist. It covers the assembly decisions that can change your postage calculation.
What about a large envelope or postcard?
A 9-by-12-inch envelope does not qualify for letter pricing, even if it contains only one sheet. A qualifying domestic large envelope, also called a flat, currently starts at $1.69 for 1 ounce. It must meet the standards for flats; a rigid or lumpy piece can need package pricing instead.
A qualifying domestic postcard currently costs $0.65. You can use one standard Forever stamp, but its $0.82 value exceeds that postage by $0.17. A card mailed inside an envelope is assessed as the finished envelope, not as an unenclosed postcard. See the USPS guide to letters and postcards for the applicable format requirements.
Do two Forever stamps cover an international letter?
Not at the current basic international rate. Two standard domestic Forever stamps total $1.64; a qualifying First-Class Mail International letter up to 1 ounce needs $1.75. That combination is $0.11 short. One Global Forever stamp covers the basic 1-ounce international letter price instead.
Heavier letters and unusual shapes need a separate calculation. Do not apply the domestic additional-ounce price to an international envelope. Use the destination and mailing date in the USPS Retail Postage Price Calculator, and check USPS international letter guidance before mailing.
Choose postage after checking the piece
Read the wording on each stamp. Standard Forever, Global Forever, Additional Ounce, and Two Ounce stamps do not all represent the same amount. If you have a mixture in a drawer, sort by postal category before adding their values.
Once you know the postage category you need, you can compare designs in our First-Class Forever stamp collection. Check the selected product's quantity and postage category before ordering. Our store FAQ covers shopping and order questions.
For an uncertain weight, unusual envelope, or package, have USPS confirm the finished piece before you stamp a batch. This guide explains published postage; it does not guarantee acceptance or delivery. Forever Stamps is an independent retailer and is not affiliated with or endorsed by the United States Postal Service.
