For a regular letter in the U.S. in 2025–2026, you usually need one Forever stamp for a standard envelope weighing up to 1 ounce, mailed within the country.

Quick Scoop: How many stamps to send a letter?

The super-short answer

  • Standard envelope, under 1 ounce, mailed within the U.S. → 1 Forever stamp.
  • Heavier letters (over 1 ounce, up to 3.5 ounces) → 1 Forever stamp + “additional ounce” postage for each extra ounce.
  • Beyond 3.5 ounces or larger, rigid, or odd-shaped mail → it’s treated more like a flat or package , and the stamp math changes.

Think of it this way: a Forever stamp is your “base ticket” for a normal letter; anything heavier or weirder needs add‑ons.

Basic rule of thumb

Most everyday letters people worry about online—birthday cards, 3–5 page letters, wedding invites—fit under 1 ounce in a standard envelope.

For U.S. domestic First‑Class Mail letters :

  • Up to 1 ounce
    • 1 Forever stamp.
  • Over 1 ounce, up to 2 ounces
    • 1 Forever stamp + 1 additional‑ounce stamp.
  • Over 2 ounces, up to 3 ounces
    • 1 Forever stamp + 2 additional‑ounce stamps.
  • Over 3 ounces, up to 3.5 ounces (max for a “letter”)
    • 1 Forever stamp + 3 additional‑ounce stamps.

If you don’t have additional‑ounce stamps, people sometimes just use extra Forever stamps and overpay a bit , which is fine but not cost‑perfect.

Typical scenarios

Here’s how this plays out in real life (and in forum discussions where people ask “Do I need one stamp or two?”):

  • 1–3 page letter in a regular envelope
    • Usually under 1 ounce → 1 Forever stamp is enough in most cases.
  • 5‑page letter in a regular envelope
    • Often still under 1 ounce with normal printer paper, so 1 Forever stamp often works, but if you add thick paper, photos, or a return envelope, you might creep over 1 ounce and need extra postage.
  • Birthday card or greeting card
    • Many cards are fine with 1 Forever stamp, but very thick or oddly shaped cards can be “non‑machinable” and need extra postage or a different rate category.
  • Postcards (within the U.S.)
    • Officially have their own cheaper postcard stamp, but you can use 1 Forever stamp and simply overpay a bit.

Why people on forums get confused

On Q&A boards and USPS‑related communities, you’ll see a lot of posts like:

“My envelope feels light; can I just slap two stamps to be safe?”

The confusion usually comes from:

  • Changing postage rates over time (the price of a Forever stamp has increased multiple times).
  • Different rules for:
    • Letters vs flats vs packages
    • Domestic vs international
    • Rigid or square envelopes vs normal rectangular ones

Some users just throw on two Forever stamps “to be sure,” which works but is more than you technically need in many cases.

Quick mini‑guide: avoid surprises

If you want to be precise rather than guessing:

  1. Check the weight
    • Use a small kitchen or digital scale if you have one; 1 ounce is about 4–5 sheets of standard printer paper plus an envelope.
  1. Check the shape
    • Standard, flexible, rectangular envelope → letter rate.
    • Very thick, square, or stiff → might not qualify as a letter and may cost more.
  1. Match stamps to ounces
    • 1 ounce → 1 Forever stamp.
    • Each extra ounce (up to 3.5 ounces) → add an additional‑ounce stamp.
  1. If in doubt
    • You can go to a post office and ask them to weigh it, or use a current online postage calculator so you don’t underpay.

SEO bits you asked for

  • Focus keyword used: “how many stamps to send a letter” appears naturally in headings and explanations.
  • Meta‑style description:
    • If you’re wondering how many stamps to send a letter in the U.S. right now, one Forever stamp usually covers a standard 1‑ounce letter, with extra postage needed only for heavier, larger, or unusually shaped mail.

TL;DR: For a normal U.S. letter in a regular envelope that doesn’t feel unusually heavy, 1 Forever stamp is almost always right , and you only start adding more when you pass 1 ounce or break the “standard letter” rules.

Information gathered from public forums or data available on the internet and portrayed here.