A stamp is proof you already paid the post office to move a piece of mail. That is the whole job. Stick one on an envelope and USPS treats that envelope as paid.
So what are stamps for, beyond that one line? They pay for weight inside one mail class: First-Class Mail letters and postcards. Distance never enters into it, a stamped letter costs the same across town or across the country.
What a stamp does not pay for is tracking, insurance, or a courier picking up a box from your porch. Those are separate products. Mixing them up is where most stamp confusion starts.
What a stamp actually pays for
What are stamps for at the most basic level? Prepaid First-Class Mail postage. Buy a Forever stamp today and it covers one ounce of a standard letter.
That holds whether you mail it this afternoon or five years from now.
USPS lists the current Forever stamp rate on its official First-Class Mail pricing page. It is $0.82 for a one ounce letter. Each extra ounce runs $0.29, and a letter tops out at 3.5 ounces before it becomes something else.
A postcard stamp runs $0.65. A metered letter costs $0.78, since a meter skips the printing cost a physical stamp carries.
Stamps are priced around letters and postcards, not boxes. That is why they get awkward the moment a package enters the picture.
If you only want the current numbers, we cover current stamp prices in full here. If you are trying to work out the quantity for a specific envelope, this guide walks through how many stamps an envelope needs. This article sticks to the simpler question: what stamps are for in the first place.
Forever stamp vs a denominated stamp
Every stamp falls into one of two buckets. The difference matters more than most buyers realize.
A Forever stamp has no dollar amount printed on it. It says ‘Forever’ because it locks in one ounce of postage no matter how many rate hikes happen after you bought it.
Buy a roll in 2022 at 60 cents. That same stamp still covers a one ounce letter today at 82 cents. You never lose value, and you never have to remember when you bought it.
A denominated stamp has a fixed price printed on the face, like a 65 cent postcard stamp. It does not adjust for future rate changes.
If the postcard rate climbs next year, a stamp printed with ’65’ is still only worth 65 cents. You would add a make up stamp for the gap.
Almost everything USPS sells at retail today is a Forever stamp. Honestly, that is the right call. Buy Forever letter stamps and you rarely think about the rate again.
Our postage price calculator tells you fast whether Forever alone covers your envelope. We go deeper on the design itself in our full breakdown of what a Forever stamp is, and if you found an old roll in a drawer, we answer whether it still works here.
When one stamp is enough
A single Forever stamp handles a standard rectangular envelope at one ounce or less. That is roughly four or five sheets of paper folded into a business size envelope. It covers most letters, cards, and bills people mail.
Heavier mail needs more. A thicker envelope needs extra ounce postage stacked on the base rate.
Shape matters too. A square card, or an envelope with a clasp or string, gets a nonmachinable surcharge because USPS equipment cannot run it the normal way. That surcharge applies even when the piece weighs under an ounce.
Large envelopes, the kind used for documents you do not want folded, have their own price table. It starts at $1.69 for the first ounce and climbs by weight to $5.24 at 13 ounces, the cap for that category.
None of this means you did something wrong. It means the piece does not match the machine sized envelope USPS built its cheapest rate around. If you are unsure, weigh it.
What a stamp does not cover
This is the other half of what are stamps for, and the part that trips up first time sellers. A stamp buys postage. It does not buy tracking, and it does not buy insurance.
A stamped First-Class letter has no tracking number. The envelope moves through the system the same way it always has. There is no scan history to pull up online.
If you need proof of delivery, Certified Mail or a tracked service is the answer, not a plain stamp.
A stamp also carries no built in insurance. If a stamped envelope gets lost, USPS has no record tying that piece to you. There is nothing to file a claim against.
Compare that to Priority Mail or Ground Advantage. Both include tracking and up to $100 of insurance in the retail price.
eBay and Etsy sellers hit this constantly. A buyer pays for tracked shipping, the seller uses a stamp on a padded envelope to save a few dollars, and now there is no tracking number when something goes wrong.
That works fine for a letter to your aunt. It is the wrong tool for anything a customer paid you to deliver.
Stamps vs a printed shipping label
| What you need | Stamp | Printed label |
|---|---|---|
| Mailing a letter or card, one ounce | Covers it | Overkill |
| Tracking number for the recipient | Not included | Included |
| Insurance if it gets lost | Not included | Usually included, up to $100 |
| Mailing a box or package | Allowed if the value covers postage, no tracking generated | Standard method, Priority Mail and Ground Advantage |
| Buying at a self service kiosk or online | Yes, at face value | Yes, at home or the counter |
You can stack enough stamps to cover a package’s postage instead of printing a label. USPS will accept it at the counter. What you will not get is a tracking barcode, since that comes from the label, not from the stamps sitting on top of the box.
Sellers on shipping forums report the same thing. A clerk weighs a stamped package, collects any difference, and takes it. The tracking number only shows up when an actual shipping label generates one.
If it were me, I would not bother with stamps on a box at all. A label from Click-N-Ship or the counter prices the package to the cent and hands you tracking for free.
Buying and using stamps the right way
Stamps are sold in books of 20, coils of 100, and single sheets. You can find them at post office counters, grocery stores, and pharmacies.
We list every place that sells them near you here. If a store trip is not happening, ordering them online works fine too.
Using one takes ten seconds. Place it in the top right corner of the envelope, address side up. Make sure the total value covers the weight and class of what you are sending.
Denominated stamps from years ago are worth their printed amount. An old one may need a cent stamp added to match today’s rate.
Not sure whether what you are holding needs one stamp, two, or a different mail class entirely? Run it through our stamp calculator before you seal the envelope.
Bottom line
A stamp is prepaid First-Class Mail postage for letters and postcards. Forever stamps hold their value no matter when the rate goes up. That is why they are the default choice for almost everyone.
What are stamps for, in one sentence? Paying for a letter to move through the mail. For a box that needs tracking, insurance, or a courier pickup, you want a shipping label and a different USPS service entirely.
