If you are mailing a standard letter with one Forever Stamp, the weight limit is 1 ounceThat single stamp — currently valued at $0.82 — covers a First-Class letter up to 1 oz, as long as the envelope meets USPS size and shape requirements. Heavier letters need additional postage, and non-standard envelopes may trigger a surcharge even if they are under 1 oz.
Current USPS letter rates
As of September 13, 2026, USPS Notice 123 lists $0.82 for an eligible stamped domestic letter up to 1 ounce, $1.11 for 2 ounces, $1.40 for 3 ounces and $1.69 for 3.5 ounces. The additional-ounce increment is $0.29, and a qualifying nonmachinable letter adds $0.49. The schedule took effect July 12, 2026.
These prices apply only after the finished piece is classified correctly. Postcards, flats, packages, international mail and added services use different rules.
Understanding the weight rules helps you avoid returned mail, unexpected surcharges, and wasted stamps. Below, we break down exactly how much weight a Forever Stamp covers, when you need extra postage, and how to plan your mailing costs as stamp prices rise.
Learn more about buying stamps →
How USPS Letter Weight Rules Work
The United States Postal Service sets weight and size limits for each mail class. For First-Class Mail letters — the category most Forever Stamps are used for — the rules are straightforward:
As long as your letter fits within those dimensions and weighs 1 oz or less, one Forever Stamp covers the full postage. If your letter exceeds 1 oz, you need additional postage based on the current per-ounce rate.
Weight Tiers and Stamp Costs
| Letter Weight | Postage Required | How to Pay |
|---|---|---|
| Up to 1 oz | $0.82 | 1 Forever Stamp |
| Over 1 oz to 2 oz | $1.11 | 1 Forever Stamp + 1 Additional Ounce stamp ($0.29) |
| Over 2 oz to 3 oz | $1.40 | 1 Forever Stamp + 2 Additional Ounce stamps ($0.65) |
| Over 3 oz to 3.5 oz | $1.69 | 1 Forever Stamp + 3 Additional Ounce stamps ($0.84) |
The maximum weight for a standard First-Class letter is 3.5 ouncesAnything heavier must be mailed as a flat (large envelope) or package, which carry different pricing structures.
How much is a Forever Stamp in 2026? →
The Non-Machinable Surcharge: When Shape Matters More Than Weight
Weight is not the only factor. Even if your letter weighs under 1 oz, USPS may charge a non-machinable surcharge of $0.49 if the envelope does not meet automated processing standards. This applies when the letter is:
- Rigid or stiff — such as an invitation with layered cardstock, ribbon, or a wax seal
- Square-shaped — a 5″ × 5″ or 6″ × 6″ envelope is not a standard letter
- Lumpy or uneven — envelopes containing keys, pens, or thick inserts
- Outside standard dimensions — too small, too large, or thicker than 0.25″
A square envelope that weighs under 1 oz still costs $1.31 to mail ($0.82 + $0.49 surcharge), not $0.82. This is one of the most common mistakes wedding invitation senders make — a beautiful square envelope needs extra postage even though it is light.
Common Scenarios and How Many Stamps You Need
| Mailing Scenario | Estimated Weight | Stamps Needed |
|---|---|---|
| Standard greeting card (flat card + envelope) | Under 1 oz | 1 Forever Stamp |
| Bill payment or check in #10 envelope | Under 1 oz | 1 Forever Stamp |
| Letter with 3–4 pages of paper | 1–2 oz | 1 Forever Stamp + 1 Additional Ounce stamp |
| Wedding invitation (flat, rectangular) | 1–2 oz | 1 Forever Stamp + 1 Additional Ounce stamp |
| Square wedding invitation (rigid) | Under 1 oz | 1 Forever Stamp + non-machinable surcharge ($0.49) |
| Holiday card with photo insert | 1–2 oz | 1 Forever Stamp + 1 Additional Ounce stamp |
Why Forever Stamp Prices Keep Rising
Forever Stamp prices have increased nearly every year since 2020. The current price is $0.82rising to $0.82 on July 12, 2026 — a 5.1% increase approved under USPS PRC Docket R2026-1. Here is how prices have changed:
Since 2020, the Forever Stamp price has risen 49% — from $0.55 to $0.82 by July 2026. USPS has cited declining mail volume and long-term financial restructuring as the primary drivers.
Learn more about the 2026 price increase →
Common Misconceptions About Forever Stamp Weight Limits
There are several misunderstandings about Forever Stamps and their weight coverage. Here are the most common ones, corrected:
Where to buy postage stamps near you →
Buying Forever Stamps at the Right Price
| Source | Price (100 stamps) | Notes |
|---|---|---|
| USPS.com / Post Office | $82.00 (face value) | Full retail price; widest design selection |
| Costco (members) | $77.75 per roll of 100 | Slight member savings; limited designs |
| Online stamp retailers | Varies (10–15% below face value) | Convenient ordering; verify unused and valid |
For households mailing holiday cards, wedding invitations, or regular business correspondence, a book of 20 stamps ($16.40) or a roll of 100 ($82.00 face value) covers most annual needs. Planning ahead means you avoid paying the higher $0.82 rate after July 12.
Frequently Asked Questions
What is the weight limit for a Forever Stamp?
One Forever Stamp covers a standard First-Class letter weighing up to 1 ounceIf your letter weighs more than 1 oz, you need to add additional ounce stamps at $0.29 each. The maximum weight for a First-Class letter is 3.5 ounces.
Do Forever stamps expire?
No — Forever Stamps never expire. They always cover the current 1 oz First-Class letter rate regardless of when you purchased them or how much you paid. Stamps bought at $0.55 in 2020 are still valid for a 1 oz letter today at the $0.82 rate.
How many Forever Stamps do I need for a 2 oz letter?
A 2 oz letter costs $1.11 in postage. The most efficient way to pay is one Forever Stamp ($0.82) plus one Additional Ounce stamp ($0.29). You could use two Forever Stamps ($1.56 total), but that overpays by $0.50.
Can I use Forever Stamps on a square envelope?
Yes, but a square envelope is considered non-machinable and carries a $0.49 surcharge. A 1 oz square envelope costs $1.31 total — one Forever Stamp ($0.82) plus the non-machinable surcharge. You can add a second Forever Stamp, but it overpays slightly.
What is the current USPS one-ounce letter rate?
The current USPS one-ounce letter rate took effect July 12, 2026 The Forever Stamp rises from $0.78 to $0.82, a 5.1% increase approved under PRC Docket R2026-1. Stamps purchased before the increase remain valid at the new rate.
Where is the cheapest place to buy Forever Stamps?
Costco sells rolls of 100 Forever Stamps for $77.75 (member price), saving about $0.25 versus face value. Online retailers may offer 10–15% below face value on larger quantities. Always confirm that stamps are unused and valid before purchasing from any source.
Sources and update note
Use the linked primary record for the exact issue, rule or current condition. Prices, availability and platform features can change and should be checked at the time of use.