Sending letters might not be as common as sending an email or text message, but there are still plenty of moments when you need good, old-fashioned snail mail — birthday cards, wedding invitations, or official documents.
And if you’ve ever stood over an envelope wondering, “Do I need one stamp or two?” — you’re not alone.
Thankfully, the US Postal Service (USPS) has made things easier with Forever Stamps, which stay valid no matter how much postage rates rise. Still, rates do change — and they did again in 2025.
So, let’s break down exactly how many stamps per ounce you’ll need this year to make sure your letter gets to its destination without delays or “Return to Sender” surprises.
How Many Stamps Per Ounce for First-Class Mail?
For most everyday letters, one Forever Stamp is enough. That single stamp covers the first ounce of a First-Class Mail letter — as long as your envelope is the right size and weight.
As of July 13, 2025, the USPS rate for a First-Class Mail letter (1 oz) is $0.78.
If your letter weighs more than one ounce, you’ll need to add extra postage for each additional ounce. You can read more about how First-Class Mail works and why it’s the go-to option for most personal mail.
2025 USPS Postage Rate Table
Here’s a simple reference table showing the latest USPS rates (effective July 2025):
| Mail Type | First Ounce Rate | Each Additional Ounce |
|---|---|---|
| Letter (stamped) | $0.78 | $0.29 |
| Letter (metered) | $0.74 | $0.29 |
| Domestic postcard | $0.61 | — |
| International letter (1 oz) | $1.70 | — |
(Source: USPS 2025 Price Adjustment)
Breaking Down “How Many Stamps Per Ounce”
Let’s make sense of those numbers with a few examples:
1 oz letter → One Forever Stamp ($0.78) ✅
1.3 oz letter → One Forever Stamp ($0.78) + $0.29 for the extra ounce → $1.07 total
2.5 oz letter → One Forever Stamp ($0.78) + $0.58 (two extra ounces) → $1.36 total
3 oz letter → Same total, $1.36
If you don’t have “extra ounce” stamps, you can just use another Forever Stamp instead — it’ll overpay slightly, but your letter will still go through without a hitch.
Want to stock up? You can buy Forever Stamps directly from the USPS store.
Forever Stamps in 2025: Still a Great Deal
The Forever Stamp has been one of the USPS’s best ideas. Once you buy it, it’s valid forever — no matter what the current postage rate is.
If you purchased a Forever Stamp years ago for $0.55, it still counts for the current $0.78 first-ounce rate today.
Just remember:
The “Forever” applies only to the first ounce of a standard letter.
If your letter weighs more, you’ll need to add $0.29 per ounce.
Oversized or rigid envelopes might cost more, even if they’re light.
How to Weigh Your Mail (and Why It Matters)
You don’t need a fancy postal scale — a simple kitchen scale works fine.
Here’s how to check your postage weight:
Seal your envelope before weighing it.
Place it on the scale and note the weight in ounces.
If it’s 1.0 oz or less, you’re all set with one Forever Stamp.
If it’s over 1.0 oz, you’ll need to add $0.29 for every extra ounce.
For example, a 1.2 oz envelope counts as 2 oz, meaning you’ll need $1.07 worth of postage.
That quick check can save you from returned or delayed mail.
Mailing Large Envelopes or Small Packages
Sometimes, your envelope doesn’t fit the “letter” category anymore. If it’s thicker, larger, or oddly shaped, the USPS considers it a large envelope (flat) or even a small package.
Here’s what that means:
A typical 4–8 oz large envelope costs around $4.26 to mail.
You can use Forever Stamps to cover that cost (around six stamps = $4.68), but it’s not always the cleanest option.
Once postage hits about $10, you’d need over 13 stamps to cover it — at that point, printed postage or a shipping label is much easier.
When in doubt, take it to your local USPS office and have them weigh it for you.
The Simple Way to Get It Right
If you’re ever uncertain about how many stamps per ounce your envelope needs, there’s one guaranteed solution:
ask your local post office.
They’ll weigh your letter, tell you the correct rate, and sell you exactly the postage you need.
It’s quick, reliable, and ensures your letter never bounces back.
The Bottom Line:
Keep a stash of Forever Stamps and a few extra-ounce stamps on hand. Know your weight, check your envelope size, and you’ll never have to guess how many stamps per ounce again.
If mailing feels like a hassle, explore US Global Mail’s virtual mailbox options — because in 2025, even your mail can go digital.
Even though we live in a digital world, knowing how many stamps per ounce you need is still a valuable skill.
A single Forever Stamp ($0.78) covers most standard letters, but once your envelope gets a little heavier, add $0.29 per extra ounce to stay compliant with 2025 USPS rates.
And if you send mail frequently — or live abroad — consider a virtual mailbox from US Global Mail. It lets you scan, forward, or manage mail online, so you never miss important deliveries again.
