Yes—an undenominated USPS stamp labeled “Additional Ounce” works like a Forever stamp for that specific price category. It remains valid and is worth the current First-Class Mail additional-ounce price when used. It is not the same as an ordinary Forever stamp for the first ounce.
Additional Ounce vs. Ordinary Forever
| Stamp | Value follows | Current value* | Main use |
|---|---|---|---|
| Ordinary Forever | First-Class Mail one-ounce stamped-letter price | 82¢ | The first ounce of a qualifying domestic letter |
| Additional Ounce | First-Class Mail additional-ounce price | 29¢ | Each added ounce on an eligible letter |
*Rates shown are effective July 12, 2026 and were checked August 31, 2026.
Does an Additional Ounce Stamp Expire?
No. A valid unused nondenominated stamp marked “Additional Ounce” continues to track the applicable additional-ounce price. Its artwork or issue year does not lock it to the price charged when it was bought.
Can You Mail a Letter with One Additional Ounce Stamp?
Not by itself at the current rate. An Additional Ounce stamp provides only the additional-ounce value. A standard two-ounce domestic letter currently needs the one-ounce price plus one additional-ounce charge:
82¢ ordinary Forever + 29¢ Additional Ounce = $1.11.
A standard three-ounce letter currently needs the one-ounce price plus two additional-ounce charges:
82¢ + 29¢ + 29¢ = $1.40.
Square, rigid, unusually thick, oversized or nonmachinable pieces can require a different surcharge. Other mail classes and international mail also use different calculations.
How to Identify the Correct Stamp
- Look for the printed words “ADDITIONAL OUNCE”.
- Do not assume that every undenominated stamp equals an ordinary Forever stamp.
- Keep it separate from Postcard, Global Forever, Nonmachinable, Two-Ounce and Three-Ounce stamps; each follows its printed price category.
Official Rule
The USPS Domestic Mail Manual, section 604, states that nondenominated stamps for the additional-ounce category remain equal to the applicable price for that category at the time of use. The current USPS stamp catalog identifies the Additional Ounce denomination as 29¢.
Related Questions
Use the postage decision guide when weight or format is uncertain, calculate how many Additional Ounce stamps equal one ordinary Forever stamp, compare current Forever stamp values, or review the one-stamp weight limit.
Answer checked August 31, 2026. The category rule is ongoing; the 29¢ amount is dynamic and should be rechecked after a USPS price change.
Compare Forever, postcard, additional-ounce, semipostal, and other postage formats in Types of Forever Stamps: A Practical Guide.