A 1.1-ounce letter needs $1.07 in postage, which works out to one Forever stamp plus one Additional Ounce stamp. If you only have Forever stamps on hand, two of them will get the letter delivered, but you’ll overpay by $0.49 and the Postal Service doesn’t refund the difference.
Why 1.1 Ounces Costs the Same as 2 Ounces
USPS rounds any fraction of an ounce up to the next whole ounce, so a letter that tips the scale at 1.1 ounces is priced as a 2-ounce letter. In 2026, First-Class Mail letter rates are $0.78 for the first ounce and $0.29 for each additional ounce or fraction of one.1USPS. Notice 123 – January 2026 Price Change – Price List Add them together and you get $1.07.
That extra tenth of an ounce isn’t a rounding error you can ignore. A second sheet of paper, a thicker card stock, or a small enclosure can push a letter past the one-ounce line, and underpaid mail either comes back to you or arrives with postage due charged to the recipient.
Stamp Combinations for $1.07
The cleanest match is one Forever stamp ($0.78) and one Additional Ounce stamp ($0.29). USPS sells Additional Ounce stamps specifically for this situation, and the denomination lines up exactly with the per-ounce surcharge.2USPS. First-Class Mail and Postage
If you don’t keep Additional Ounce stamps around, two Forever stamps total $1.56. That covers the postage with $0.49 to spare. USPS doesn’t give change on overpaid mail, so the extra just goes to the Postal Service. For a one-time letter that’s a fair trade for not making a stamp run. If you send several slightly-over-an-ounce letters a month, a sheet of Additional Ounce stamps pays for itself quickly.
When Two Forever Stamps Become the Right Answer
Some 1.1-ounce letters carry a non-machinable surcharge of $0.49, which brings the total to $1.56, the exact cost of two Forever stamps.1USPS. Notice 123 – January 2026 Price Change – Price List The surcharge applies when the envelope can’t run through automated sorting equipment. Common triggers include:
- A square envelope, or a rectangle with an unusual aspect ratio (length divided by height under 1.3 or over 2.5)
- Rigid or lumpy contents like pens, keys, or loose coins
- Clasps, strings, or buttons used as closures
- Plastic wrapping
- An envelope too stiff to bend around sorting rollers
Wedding invitations, gift cards in bulky packaging, and anything with a wax seal usually fall into this category. If any of that describes your letter, two Forever stamps land on $1.56 exactly.
Make Sure It Still Qualifies as a Letter
Postage only works if the envelope is actually a letter by USPS definitions. Letters must be rectangular and fall inside these limits:3USPS. Sizes for Letters – Postal Explorer
- Between 3½ and 6⅛ inches tall
- Between 5 and 11½ inches long
- Between 0.007 and ¼ inch thick
- No more than 3.5 ounces
Anything outside those dimensions is reclassified as a large envelope or a parcel. A 2-ounce large envelope costs $1.90 rather than $1.07, so an oversized greeting card envelope can nearly double your postage even at the same weight.1USPS. Notice 123 – January 2026 Price Change – Price List
International 1.1-Ounce Letters
If the letter is leaving the country, domestic rates don’t apply. First-Class Mail International charges $1.70 for the first ounce to any destination, and a 1.1-ounce letter is priced as 2 ounces:1USPS. Notice 123 – January 2026 Price Change – Price List
- Canada: $2.00
- Mexico: $2.55
- Most other countries: $3.40
A Global Forever stamp covers only the first ounce.4USPS. 2026 Postage Price Change The additional-ounce charges vary by destination and don’t line up with domestic Additional Ounce stamps, so for international mail with any extra weight it’s easier to have a postal clerk weigh and price the letter at the counter.
If you’re not sure whether your envelope is actually over an ounce, a kitchen scale accurate to 0.1 ounces will tell you. The difference between one stamp and two comes down to that fraction, and it’s cheaper to check than to have the letter returned.