You're standing at the kitchen counter, wedding invitations in one hand and a digital scale in the other. The numbers flicker and settle: 1.1 ounces.
Shoot.
That tiny fraction of an ounce just turned your standard Forever stamp into a "don't you dare drop this in the blue box yet" situation. If you do, it’s coming back with a "Postage Due" stamp that looks like a scarlet letter. Or worse, your guests get stuck paying the difference. Most people just slap a second Forever stamp on the envelope and call it a day. Honestly? That's exactly what the USPS wants you to do, but it’s a total waste of money.
The current 2nd ounce stamp cost is 29 cents.
If you use two Forever stamps (which cost 78 cents each as of early 2026), you’re spending $1.56 to mail a letter that should only cost $1.07. You are basically handing the government a 49-cent tip. Every. Single. Time.
The Math Behind the Extra Weight
Postage isn't just one flat rate. It’s a tiered system, and the "additional ounce" is the unsung hero of the mailing world.
Back in 2024, we saw the rate for that extra ounce jump to 28 cents. Then, in July 2025, it ticked up again to the current 29 cents. Postmaster General David Steiner recently confirmed there won't be another hike in January 2026, so we’re riding with these numbers for a while.
Here is how the breakdown looks for a standard letter:
- 1 Ounce: $0.78 (One Forever Stamp)
- 2 Ounces: $1.07 (One Forever Stamp + one 29-cent "Additional Ounce" stamp)
- 3 Ounces: $1.36
- 3.5 Ounces: $1.65
Wait, why 3.5? Because once a letter hits 3.5 ounces, it's no longer a "letter" in the eyes of the USPS. It becomes a "Large Envelope" (a flat) or a parcel. The rules change. The price jumps. It’s a whole different ballgame.
Those Purplish School Bus Stamps
You've probably seen them. They often have a school bus on them or some other simple design. They don't say "29 cents" on them. Instead, they just say "Additional Ounce." These are beautiful.
They are "Forever" stamps in their own right, but for the weight, not the base rate. If you buy a sheet of additional ounce stamps today for 29 cents and the price goes up to 32 cents next year, your old stamps still cover that second ounce. It's a hedge against inflation for people who mail heavy stuff like RSVP cards, legal documents, or those thick "Year in Review" Christmas letters.
When "Weight" Isn't the Only Problem
I once mailed a square envelope. Just a simple, square birthday card. I used a Forever stamp and a 29-cent stamp. It still came back.
Why? Because the Post Office hates squares.
If your envelope is square, too rigid (like it has a wooden nickel inside), or has "clasp" closures, it’s considered non-machinable. The machines that sort mail at lightning speed can't handle it. This triggers a "Non-machinable Surcharge."
In 2026, that surcharge is 49 cents.
So, if you have a 1.2-ounce wedding invitation that is also square, you need:
- The first ounce ($0.78)
- The second ounce ($0.29)
- The square surcharge ($0.49)
Your total is $1.56. In this one specific case, using two Forever stamps actually works out perfectly. But only because you’re being penalized for the shape, not just the weight.
Real-World Nuance: The "Metered" Loophole
If you're running a small business or have access to a postage meter (like Pitney Bowes or even some online services), you aren't paying 78 cents for that first ounce.
You’re paying 74 cents.
The 2nd ounce stamp cost remains the same for metered mail (29 cents), but your starting point is lower. It doesn't sound like much until you’re sending out 500 invoices. Then it's the difference between a nice lunch and... not a nice lunch.
Common Misconceptions
- "I can just use two postcard stamps." Nope. Postcard stamps are 61 cents. Two of them equal $1.22. That covers a 2-ounce letter ($1.07), but you're still overpaying by 15 cents.
- "The 2nd ounce is cheaper if I use a 'Butterfly' stamp." The "Non-Machinable Butterfly" stamps are currently valued at $1.27. These are designed to cover a 1-ounce letter that is square or rigid. If your letter is 2 ounces and square, the Butterfly stamp isn't enough. You'd still need an extra 29-cent stamp.
How to Check Your Weight at Home
Don't guess.
If you don't have a mail scale, a standard kitchen scale works fine. Just make sure it’s set to ounces, not grams.
A standard sheet of printer paper and a business envelope usually weigh about 0.18 ounces. You can typically fit about four or five sheets of paper in an envelope before you even have to worry about the 2nd ounce stamp cost. But add a cardstock insert or a few photos? You'll hit that 1.1-ounce mark faster than you think.
Actionable Steps for Your Next Mailing
If you’re prepping a big batch of mail, don't just wing it.
First, take one fully assembled envelope to the counter at the Post Office. Ask them to weigh it and "check for non-machinable characteristics." This is free. They will tell you exactly what it costs.
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Second, buy the specific stamps you need. If it’s a 2-ounce letter, buy a book of Forevers and a sheet of "Additional Ounce" stamps. You'll save nearly $10 for every 20 letters you mail compared to using two Forever stamps.
Finally, if you find yourself constantly at 1.1 ounces, consider your paper choice. Switching from 32lb bond paper to 24lb paper can often drop a letter back under the 1-ounce limit, saving you the 29-cent "heavy" tax entirely.