Yes. You can use additional ounce stamps by themselves as long as the total postage you affix covers the current USPS rate for that mailpiece and any required surcharge. For a standard 1-ounce First-Class Mail letter after the July 12, 2026 price change, three 29-cent additional-ounce stamps equal 87 cents, which covers the current 82-cent retail letter rate, though you would overpay by 5 cents.
This refresh is a USPS policy update based on current primary sources, not a counter test at a retail window.
Table Of Contents
Quick answer
The key rule is on the current Domestic Mail Manual section on postage payment: the total postage affixed must equal at least the postage charge required for the mailpiece. USPS also sells the current School Bus additional-ounce stamp as a non-denominated stamp that stays valid for the additional-ounce rate. Put those two rules together and the answer is yes, if the math works.
How USPS treats the stamp
The current USPS store page for the School Bus additional-ounce stamp says it is a non-denominated stamp used for everyday mail, that it covers the amount or weight printed on it, and that it remains valid even if rates increase. The current Notice 123 price list and USPS First-Class Mail FAQ show that the retail First-Class Mail letter rate is now 82 cents for 1 ounce and 29 cents for each additional ounce, effective July 12, 2026.
When using additional ounce stamps alone works
| Mailpiece | Current postage due | Additional-ounce stamps only | Result |
|---|---|---|---|
| 1-ounce stamped letter | $0.82 | 3 stamps = $0.87 | Works, but overpays by $0.05. |
| 2-ounce stamped letter | $1.11 | 4 stamps = $1.16 | Works, but overpays by $0.05. |
| 3-ounce stamped letter | $1.40 | 5 stamps = $1.45 | Works, but overpays by $0.05. |
| Postcard | $0.65 | 3 stamps = $0.87 | Works on value, but wastes postage. |
That table is an inference from the current retail prices in Notice 123 plus the rule that total postage affixed must cover the required amount.
When it does not work
Using only additional-ounce stamps fails whenever the total value is too low or the mailpiece needs more than ordinary letter postage. Two 29-cent stamps total 58 cents, so they do not cover a current 1-ounce stamped letter. You also need extra postage if the piece is nonmachinable, qualifies as a flat, includes extra services, or otherwise prices above the simple letter rate. In those cases, the USPS FAQ and DMM rules say the total must still meet the full required amount.
Size and shape rules still matter
The current USPS retail physical standards say a letter-size piece must be at least 5 by 3.5 inches, no more than 11.5 by 6.125 inches, no more than one-quarter inch thick, and no more than 3.5 ounces. If it exceeds those limits, it can move into flat pricing. USPS also says pieces over 6 inches long or 4.25 inches high need at least 0.009 inch thickness to avoid certain nonmachinable treatment.
Common mailpieces that change the math
USPS treats many seemingly simple cards and envelopes as more expensive than a plain machinable letter. The current nonmachinable criteria include square or oddly proportioned letters, rigid pieces, clasps or strings, plastic wrapping, and uneven contents such as coins or keys. The First-Class Mail FAQ also reminds customers that size, shape, and nonmachinable status affect price. So yes, additional-ounce stamps can work by themselves, but not if you ignore the mailpiece itself.
When to use the calculator instead of guessing
If your piece is heavy, rigid, decorative, square, or close to the letter-size limit, use the official USPS Retail Postage Calculator. USPS points customers to that calculator both on the additional-ounce stamp product page and in the First-Class Mail FAQ. That is the safest path whenever your mail is not a plain, rectangular letter.
Bottom line
You can use additional ounce stamps by themselves, but only because USPS postage is additive and the total value is what matters. As of the current July 12, 2026 price list, three 29-cent additional-ounce stamps cover a 1-ounce stamped letter, four cover 2 ounces, and five cover 3 ounces. Just remember that shape, rigidity, and surcharges can change the required amount fast.