A First-Class Mail Forever stamp costs $0.82, which is the current one-ounce letter price, and USPS states it will never expire even if the letter rate goes up. Stamps stay the cheap answer right until a piece stops being a letter or a flat, and USPS draws those two ceilings at 3.5 oz and 13 oz. We should be blunt about our own scope here: SMKlog sells domestic parcel labels, not postage stamps, not mailbox rentals, and nothing that crosses a border.
Letters stop at 3.5 oz and large envelopes at 13 oz. Past those, USPS prices the piece as a package.
These come straight out of the USPS price list rather than from anybody's summary of it. Stamped and metered postage are priced differently, which surprises people who have only ever bought stamps.
| Piece | Weight | Retail price |
|---|---|---|
| Letter, postage stamps | 1 oz | $0.82 |
| Letter, postage stamps | 2 oz | $1.11 |
| Letter, postage stamps | 3 oz | $1.40 |
| Letter, postage stamps | 3.5 oz, the maximum | $1.69 |
| Letter, metered postage | 1 oz | $0.78 |
| Letter, metered postage | 3.5 oz | $1.65 |
| Non-machinable surcharge | Any letter that trips it | $0.49 |
| Postcard, standard size | Up to the postcard limit | $0.65 |
The steps between those stamped rows are all the same size. Subtract $0.82 from $1.11 and the additional ounce comes to $0.29, and that same 29 cent step carries the price to $1.69 at 3.5 oz. A pack of stamps is priced by simple multiplication of the count printed on it, so at the July 12, 2026 rate a 20 stamp book comes to $16.40 of face value.
A Forever stamp carries no printed value. It carries an entitlement, and USPS puts it in one sentence on its own First-Class Mail page: First-Class Mail Forever stamps cost $0.82 (the current 1 oz price) and will never expire, even if the First-Class postage rate goes up.
Three consequences follow from that. Stamps bought years ago at a lower price still pay today's one-ounce letter rate, so a drawer full of them is worth more than it cost. A stamp printed with a dollar amount is worth that amount and no more, so old denominated stamps are combined with extra postage to reach the current price rather than being thrown out. And a rate rise never strands anyone who bought ahead, which is the entire point of the design.
Buying them is the least interesting part. USPS sells stamps at Post Office counters and through its own store at usps.com, and plenty of supermarkets and pharmacies resell them at face value. There is no legitimate reason for a seller to be offering current stamps below face value, and that is the one signal worth treating as a warning.
USPS puts two hard numbers on its own page: Maximum weight for First-Class Mail letters is 3.5 oz, and for large First-Class Mail envelopes, the maximum weight is 13 oz. Above 13 oz, or as soon as a piece is rigid and boxy rather than flat and bendy, it prices as a package. There is a second, quieter cutoff too, because USPS states that mailpieces weighing more than 10 oz bearing only stamps as postage are not eligible for its free package pickup.
So the sensible question stops being how many stamps and becomes what a package label costs. Here is the smallest box in our own test set, priced on a real lane.
| Carrier | Service | Price | Transit window returned |
|---|---|---|---|
| USPS | Ground Advantage | $8.86 | 8-9 business days |
| FedEx | Ground Economy | $10.06 | 6-7 business days |
| UPS | Ground | $10.31 | 2-3 business days |
| UPS | 3 Day Select | $15.13 | 5-6 business days |
| UPS | 2nd Day Air | $15.38 | 2-3 business days |
Notice the gap between the two worlds. A 6 oz flat document envelope is priced in single dollars under the letter rules, while an 8 oz box on the same day cost $8.86 at the cheapest. That is not a markup, it is a different product with tracking and a different network behind it, and the honest advice is to keep flat paper in the mail stream and put objects on a package label. For a parcel that outgrows the parcel network entirely, USPS caps packages at 70 lb and 130 inches of length plus girth, and past that our freight review form is the right door. The wider question of what a label costs, service by service, is laid out in what a shipping label actually costs.
Square envelopes, rigid ones, anything with a clasp or an uneven lump inside can trip the $0.49 non-machinable surcharge. It applies per piece, so on a hundred invitations it is a $49 line item that most people find out about at the counter.
The one-ounce letter is $0.78 metered against $0.82 stamped, and the gap holds all the way up the ladder. On a handful of letters it is noise. On a monthly mailing it is the reason businesses run a meter at all.
The $0.65 rate belongs to standard-sized rectangular postcards. Oversized or oddly proportioned cards fall out of that rate and get priced as letters, sometimes with the non-machinable surcharge on top.
$0.82, which USPS describes as the current 1 oz price. That figure comes from Notice 123 with prices effective July 12, 2026, and from the USPS First-Class Mail page, both read on 2026-07-28.
USPS says they do not. Its own wording is that Forever stamps will never expire, even if the First-Class postage rate goes up, which is what makes a stamp bought at an older price still good for a one-ounce letter today.
Face value is the count on the pack multiplied by the single stamp price. At the July 12, 2026 rate of $0.82, a book of 20 works out at $16.40. Packs are sold in several counts, so check the number printed on the one in front of you before doing the sum.
USPS caps First-Class Mail letters at 3.5 oz and large envelopes at 13 oz. Above that, or as soon as the item is a rigid object rather than a flat piece, it is priced as a package. On 2026-07-28 an 8 oz box from Newark to Atlanta quoted $8.86 at the cheapest, with tracking included.