Postage mistakes happen more often than people expect. A letter comes back marked postage due, or a package sits at the post office because it needed more than one stamp. This guide breaks down exactly how many Forever Stamps you need for common mail types in 2025, so your mail gets where it is going the first time.
Why the Number of Stamps You Need Can Change
A Forever Stamp always covers a standard one ounce First-Class letter. Once your mail goes past that weight, shape, or size, the postage requirement changes.
A few factors affect how many stamps you need:
- The total weight of the envelope or package
- Whether the item is a letter, large envelope, or package
- The shape of the envelope, since square or odd shapes cost more
- Whether you are mailing domestically or internationally
Knowing these factors ahead of time keeps your mail moving without delays.
How Many Stamps for a Standard Letter
Most letters only need one Forever Stamp.
Use this guide for letters:
- A standard envelope weighing one ounce or less needs one stamp
- Each additional ounce needs one extra ounce stamp
- A typical letter with two or three sheets of paper usually stays under one ounce
- Heavier paper, extra pages, or enclosures like photos can push a letter over one ounce
If your letter feels thick or heavy in your hand, weigh it before mailing to avoid a returned piece.
How Many Stamps for a Postcard
Postcards use a separate, lower rate than letters.
Postcard basics to know:
- A standard size postcard needs one postcard stamp, not a full letter stamp
- Oversized postcards may be charged at the letter rate instead
- A Forever Stamp meant for letters can be used on a postcard, but it costs more than needed
- Postcard rates change independently from letter rates during a price increase
Buying dedicated postcard stamps saves money if you send cards often, such as for holidays or greeting card business use.
How Many Stamps for a Large Envelope or Flat
Large envelopes, also called flats, follow different rules than standard letters.
A mail piece is usually considered a large envelope if it is:
- Larger than a standard number 10 envelope
- Rigid or contains bulky contents
- Over 3.5 ounces in weight
- Sent flat rather than folded
Large envelopes need a large envelope rate stamp or the correct combination of postage, not a single Forever Stamp.
How Many Stamps for a Package
Packages almost always need more postage than a single stamp can cover.
Packages typically require:
- Weight-based postage calculated at the counter or online
- A parcel or Priority Mail rate instead of a letter rate
- Stamps only as a partial payment method, combined with additional postage
- Proper packaging to avoid delays from damaged labels or seals
For most packages, buying postage online or at the counter is faster and more accurate than combining loose stamps.
Quick Reference Chart for 2025
Use this simple breakdown before you mail:
- Standard letter, one ounce or less: one Forever Stamp
- Standard letter, over one ounce: one Forever Stamp plus additional ounce stamps
- Standard postcard: one postcard stamp
- Large envelope or flat: large envelope rate, not a single letter stamp
- Package: weight based postage, stamps alone usually not enough
Keeping a small kitchen scale near your mail area makes this process much easier.
Common Mistakes That Lead to Postage Due Notices
Postage due notices are avoidable in almost every case.
These mistakes cause most returned or delayed mail:
- Using one Forever Stamp on a heavy or thick envelope
- Assuming a postcard needs the same postage as a letter
- Sending oddly shaped envelopes without extra postage
- Trying to cover a package with several letter stamps instead of proper postage
- Not accounting for enclosures like extra paper, cards, or small items
Checking weight and shape before you seal an envelope prevents almost all of these issues.
Stock Up on the Right Stamps for Your Mailing Needs
Since letter and postcard rates can shift with a price increase, keeping a coil of Forever Stamps on hand helps you avoid running out at the wrong time. A coil of 100 covers months of regular mailing for most households and small offices.
You can view current in-stock Forever Stamp coils here.
FAQs
How many Forever Stamps do I need for a normal letter?
One Forever Stamp covers a standard letter weighing one ounce or less. Anything heavier needs an additional ounce stamp for each extra ounce.
Can I use a Forever Stamp on a postcard?
Yes, but it covers more postage than a postcard actually needs. A dedicated postcard stamp is a better value if you mail postcards often.
How do I know if my envelope needs extra postage?
Weigh the envelope and check its shape. Anything over one ounce, square shaped, or rigid usually needs more than a single Forever Stamp.
Can I use Forever Stamps to mail a package?
Stamps can be used as partial postage on some packages, but most packages need weight based postage instead of loose stamps.
Do postcard stamps cost the same as letter stamps?
No. Postcard stamps are priced lower than letter stamps and are meant only for standard size postcards, not letters or large envelopes.