How Many Stamps Do I Need to Mail a Letter? 2025 Guide
Quick Answer
- 1 ounce or less: 1 Forever Stamp ($0.78)
- 2 ounces: 1 Forever + 1 additional ounce stamp ($1.07 total)
- 3 ounces: 1 Forever + 2 additional ounce stamps ($1.36 total)
Stamp prices changed again in 2025 — but figuring out how many stamps you need is straightforward. Here are clear tables by weight, plus common alternatives to adhesive stamps. Or skip stamps entirely and send mail online with automatic postage calculation. For important documents, use our online letter service with tracking included.
Stamp Calculator (Estimate)
Get a quick estimate of how many stamps you'll need. This is a guide only—USPS is the final word on postage.
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This calculator is for educational purposes and uses the same example rates shown in this guide. Always confirm exact postage with USPS for time-sensitive or high-value mail.
How Many Stamps Do You Need by Letter Weight (2025)
| Letter Weight | Stamps Needed | Total Cost |
|---|---|---|
| 1 ounce or less | 1 Forever Stamp | $0.78 |
| 2 ounces | 1 Forever + 1 Additional Ounce | $1.07 |
| 3 ounces | 1 Forever + 2 Additional Ounce | $1.36 |
| 3.5 ounces (max for letter) | 1 Forever + 3 Additional Ounce | $1.65 |
💡 Stamp Tip
Additional ounce stamps cost $0.29 each. You can buy them at post offices or use multiple Forever Stamps if needed (though it'll cost more than the exact postage). For heavier letters or documents, use our print and mail service to handle postage automatically.
Note: Postage rates can change. Always confirm current prices with USPS if your letter is time-sensitive or high-value.
What Counts as Additional Ounces When Calculating Stamps?
Common items that add weight to your letter:
- Multiple pages (5+ sheets of paper)
- Photos or cards
- Thick envelopes or padding
- Return envelopes included
- Small items like USB drives or keys
How Many Stamps for Special Situations
Large or Non-Standard Envelopes
If your envelope is larger than 6⅛" × 11½" or thicker than ¼", it requires large envelope postage starting at $1.63, regardless of weight.
Non-Machinable Letters (Rigid, Square, or Bulky)
Letters that cannot be processed by USPS sorting machines require a $0.49 non-machinable surcharge in addition to regular postage. This applies to:
- Square envelopes (common for wedding invitations)
- Rigid or thick cards that don't bend easily
- Envelopes with clasps, string ties, or buttons
- Wax seals or bulky decorations
- Items inside that make the envelope lumpy (keys, USB drives, etc.)
Total cost for a 1-ounce non-machinable letter: $1.27 (1 Forever Stamp + $0.49 surcharge)
International Letters
International letters require Global Forever Stamps ($1.70) or equivalent postage, regardless of destination country.
Certified Mail
For important documents, add Certified Mail. The Certified Mail service fee is $5.30 (plus regular postage). Optional receipts: Electronic Return Receipt $2.82 or the paper "Green Card" $4.40. You can also send Certified Mail online without visiting the post office.
Examples: How Many Stamps for Common Letters
Here are real-world scenarios to help you determine the right postage:
2-page letter in standard envelope
1 Forever Stamp ($0.78) — Most 1-3 page letters weigh under 1 ounce
6-page letter with return envelope
1 Forever + 1 Additional Ounce ($1.07) — This typically weighs 1-2 ounces
Letter with photo
1 Forever + 1-2 Additional Ounce ($1.07-$1.36) — Photos add weight to standard letters
Standard greeting card
1 Forever Stamp ($0.78) — Most flat greeting cards under 1 oz; rigid cards need non-machinable surcharge
Thick greeting card or invitation
1 Forever + $0.49 non-machinable surcharge ($1.27 minimum) — Rigid or square envelopes need extra postage
How to Determine Your Letter Weight
Without a postal scale:
- 1-5 sheets of paper: Usually under 1 ounce
- 6-10 sheets: Likely 1-2 ounces
- Thick envelope or contents: Probably over 1 ounce
- When in doubt: Add extra postage or visit a post office
FAQs
What happens if I don't use enough stamps?
Your letter will be returned to you marked "postage due" or the recipient may have to pay the missing postage to receive it.
Can I use multiple Forever Stamps instead of additional ounce stamps?
Yes, but it's more expensive. Two Forever Stamps ($1.56) cost more than one Forever Stamp plus one additional ounce stamp ($1.07).
Do I need special stamps for important documents?
No special stamps, but consider Certified Mail for legal documents, tax forms, or other important correspondence to ensure secure delivery.
How can I mail a letter online without stamps?
You can generate mailable postage via approved PC-postage/meter solutions, self-service kiosks, or an online upload tool. See how to mail a letter online for options.
Prefer a digital workflow? You can upload a letter instead of using stamps.
Open upload toolOr use our online mailing service for bulk letters and automated postage.
Want to learn more? Check out our complete guides on letter mailing costs and how to mail a letter step-by-step.
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