You’re standing at your kitchen counter, wedding invitations or a thick stack of tax documents in hand, wondering if a single Forever stamp is going to cut it. It usually doesn't. We’ve all been there, hovering over a digital scale or just "eyeballing" the weight of an envelope, fearing the dreaded "Return to Sender" stamp because we were off by a fraction of an ounce.
Honestly, the cost of extra ounce stamp is one of those tiny life details that feels irrelevant until you’re at the post office and the line is twenty people deep.
As of January 2026, the price to add that extra weight to your First-Class mail is $0.29.
If you haven't checked the rates since last summer, you might be surprised. The United States Postal Service (USPS) held rates steady for the start of 2026, which is a rare bit of breathing room after the flurry of hikes we saw in 2024 and 2025. Postmaster General David Steiner and the Board of Governors decided to forgo a January increase for "Market Dominant" products—that’s postal-speak for your standard letters and postcards.
Why the Cost of Extra Ounce Stamp Is Fixed (For Now)
Postage prices have been on a roller coaster. In July 2025, we saw the standard First-Class 1-ounce letter jump to $0.78. Along with that, the "additional ounce" rate ticked up to $0.29.
While shipping services like Priority Mail and Ground Advantage saw their annual price adjustments on January 18, 2026, standard stamps were spared. This means if your letter weighs 1.1 ounces, you aren't just slapping on two Forever stamps. That would be a waste of money. Two Forever stamps would cost you $1.56, whereas a 2-ounce letter actually only costs $1.07 ($0.78 for the first ounce + $0.29 for the second).
Basically, you’re overpaying by nearly 50 cents if you don't use the correct "Additional Ounce" postage.
The School Bus Stamp and Other Variations
Most people don't realize there is actually a specific stamp for this. It’s often called the "School Bus" stamp because, for years, the design featured a classic yellow bus. It doesn't have a denomination printed on it (just like a Forever stamp), but it specifically covers that extra ounce.
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- The 2-Ounce Stamp: Often used for wedding invitations, currently valued at $1.07.
- The 3-Ounce Stamp: Valued at $1.36.
- The Non-Machinable Surcharge: This is the "hidden boss" of postage. If your envelope is square, too rigid, or has a clasp, you’ll pay $1.27 for the first ounce regardless of weight.
Doing the Math: When Does It Get Complicated?
Let’s say you’re mailing a 3.2-ounce letter. USPS rounds up. Anything over 3 ounces but under 4 ounces is billed at the 4-ounce rate.
Calculation: $0.78 + (3 \times $0.29) = $1.65$.
Wait, there’s a catch. First-Class Mail letters only go up to 3.5 ounces. If your "letter" hits 3.6 ounces, it’s no longer a letter in the eyes of the government. It becomes a "Large Envelope" (Flat).
Flats have a totally different pricing structure. A 1-ounce Flat starts at $1.63. Each additional ounce for a Flat is also $0.29. So, if you try to stuff a 4-ounce stack of paper into a standard #10 envelope, you're going to have a bad time. Not only will it probably rip, but the postage will jump significantly because of the weight-to-shape ratio.
Common Misconceptions About Postage
"Can't I just use two 1-cent stamps?" Sure, if you have 29 of them.
The USPS sells stamps in all sorts of denominations—1, 2, 3, 5, and 10 cents—specifically so you can make up the difference when rates change. But most people find it way easier to just buy a sheet of the $0.29 additional ounce stamps and keep them in a drawer.
Another big one: "The Forever stamp covers any letter." Nope. It covers the first ounce of a standard-sized, rectangular envelope. If you're sending a thick "thank you" card with a wax seal, that seal makes the envelope "non-machinable." The machines can't zip it through the rollers. That adds a surcharge, even if it weighs less than an ounce.
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Real-World Example: The Wedding Invitation Dilemma
I once saw a bride-to-be buy 200 beautiful, heavy-stock invitations. They were square. Square is the enemy of cheap postage.
Because they were square, they required the non-machinable surcharge. Because they had a thick liner and a RSVP card, they weighed 1.2 ounces.
Cost per invite:
- First ounce (non-machinable rate): $1.27
- Second ounce: $0.29
- Total: $1.56
If she had just used a standard Forever stamp, 200 of her closest friends would have received "Postage Due" notices. That's not exactly the vibe you want for your big day.
How to Save on Postage Costs in 2026
If you’re a small business owner or just someone who mails a lot, those 29-cent increments add up.
Metered Mail: If you use a postage meter (like Pitney Bowes or an online service like Stamps.com), the first ounce is actually cheaper—$0.74 instead of $0.78. However, the cost of extra ounce stamp usually remains the same at $0.29 for both retail and metered.
Watch the Shape: Keep it flat. Keep it flexible. If you can't bend the envelope easily, you’re paying the package or non-machinable rate.
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The "Standard Letter" Rule: * Minimum height: 3.5 inches.
- Maximum height: 6.125 inches.
- Maximum thickness: 0.25 inches.
If your letter is thicker than a quarter-inch, it’s not a letter anymore. It’s a flat or a parcel.
Actionable Steps for Your Next Mailing
Don't guess. Seriously.
First, get yourself a small digital kitchen scale. They cost about $10 and will save you three times that in returned mail or wasted stamps within a year.
Second, if you're unsure about the cost of extra ounce stamp for a specific item, check the USPS Postal Explorer website. It’s the "source of truth" for every weird shipping edge case.
Third, if you have old "Additional Ounce" stamps from 2023 when they were worth 24 cents, they are still valid—you just have to add "make-up" postage. You’d need to add a 5-cent stamp to that old 24-cent bus stamp to reach the current 29-cent requirement.
Lastly, remember that postage rates are scheduled to be reviewed again for mid-2026. While we have a reprieve right now, the "Delivering for America" plan often involves twice-yearly adjustments. Stocking up on Forever stamps is a hedge against the first ounce going up, but since "Additional Ounce" stamps are usually sold at their face value and aren't always "Forever" style (though some are), you should always check the denomination before you lick and stick.
Keep your envelopes thin, your scales calibrated, and your 29-cent stamps ready.