How Many Forever Stamps Do I Need for a Letter?

One of the most common postage questions is also one of the simplest: how many Forever Stamps do you need to mail a letter?

For a standard First-Class Mail letter within the United States, one Forever Stamp is generally used for a 1-ounce rectangular envelope. That covers many everyday letters, greeting cards, invoices, thank-you notes, and simple announcements.

When one Forever Stamp is usually enough

• A standard letter in a regular rectangular envelope
• A short greeting card or thank-you note
• A business letter, invoice, or simple document mailing
• Most lightweight personal letters mailed within the United States

When you may need extra postage

You may need additional postage if your envelope is heavier than 1 ounce, unusually shaped, rigid, square, oversized, or thicker than a normal letter. Wedding invitations, photo cards, layered stationery, and envelopes with inserts often need extra attention.

If you are not sure, weigh the envelope before mailing or ask your local post office to confirm the correct postage. This is especially helpful before sending a large batch of invitations or business mail.

Smart mailing tips

• Keep envelopes flat, flexible, and rectangular when possible.
• Use a kitchen or postal scale for large batches.
• Test one finished envelope before mailing hundreds of pieces.
• Keep extra Forever Stamps on hand for regular mail needs.

Tool Stamps offers genuine USPS Forever Stamps for customers who mail letters, cards, invitations, announcements, and business correspondence across the United States. You can browse popular options in our Flag Stamps, Love Stamps, and All Stamps collections.