The short answer
Mailing a standard letter of up to 1 ounce in the US costs $0.82, the price of one First-Class Mail Forever stamp, effective July 12, 2026. Each additional ounce adds $0.29 up to 3.5 ounces, so a 2-ounce letter costs $1.11 and a 3.5-ounce letter costs $1.69. Square, rigid, or lumpy envelopes add a $0.49 nonmachinable surcharge, and large envelopes start at $1.69. USPS adjusts prices periodically, so check the current price list before you buy in bulk.
What a stamp costs in 2026
A First-Class Mail Forever stamp costs $0.82. USPS raised it from 78 cents to 82 cents on July 12, 2026, and that price pays for one rectangular, standard-size letter weighing up to 1 ounce to any US address, including US territories and military addresses.
Forever stamps do not show a price and never expire. A Forever stamp you bought for 78 cents, or for much less years ago, still covers the full 1-ounce letter price today. That makes them the simplest stamps to keep at home, because a price change never leaves you with stamps that suddenly fall short.
Businesses that use a postage meter pay a slightly lower metered letter price, $0.78 for 1 ounce. Everyone else buying stamps at a Post Office, a retailer, or the USPS Postal Store pays the stamped price shown in this guide.
Letter postage by weight
Letter postage is charged by weight in steps, and each price covers mail weighing not over the stated amount. A letter that weighs 1.2 ounces pays the 2-ounce price. These are USPS retail prices for stamped letters, effective July 12, 2026.
Above 3.5 ounces, a letter no longer qualifies for letter prices even if it still fits in a regular envelope. USPS charges large-envelope (flat) prices instead, so a 4-ounce letter in a business envelope costs $2.56, not $1.98.
| Weight not over | Postage | Using Forever stamps only | Exact stamp combination |
|---|---|---|---|
| 1 oz | $0.82 | 1 Forever stamp ($0.82) | 1 Forever stamp |
| 2 oz | $1.11 | 2 Forever stamps ($1.64) | 1 Forever stamp + 1 additional-ounce stamp |
| 3 oz | $1.40 | 2 Forever stamps ($1.64) | 1 Forever stamp + 2 additional-ounce stamps |
| 3.5 oz | $1.69 | 3 Forever stamps ($2.46) | 1 Forever stamp + 3 additional-ounce stamps |
How many stamps do I need for a letter?
One Forever stamp is enough for most personal letters. USPS’s rule of thumb is that about four sheets of ordinary 8.5 × 11 inch printer paper in a rectangular business-size envelope weigh about 1 ounce. A greeting card in a matching envelope usually falls in that range too, unless it is square or has something attached.
If you are close to the limit, weigh the sealed envelope instead of guessing. A kitchen scale works, and you can also use a postal scale, a self-service kiosk, or the Post Office counter. Because prices step up at each ounce, a letter that weighs even slightly more than 1 ounce needs $1.11 in postage.
When a letter needs two ounces of postage, two Forever stamps will cover it, but you pay $0.53 more than the $1.11 required. To pay closer to the exact amount, combine a Forever stamp with additional-ounce stamps, which USPS prices at the current additional-ounce rate of $0.29, or with low-value 1¢ to 10¢ stamps from the Postal Store.
- Up to about four sheets of paper in a standard envelope: 1 Forever stamp.
- Five to about seven sheets: weigh it; up to 2 ounces needs $1.11 in postage.
- Any square, rigid, or lumpy envelope: add the $0.49 nonmachinable surcharge.
- Put the stamps in the upper-right corner of the envelope, on the address side.
How many pages can you mail with one stamp?
About four sheets of ordinary printer paper, folded into a standard business envelope, stay within the 1-ounce limit that one $0.82 Forever stamp covers. A fifth sheet may or may not fit, depending on the paper and the envelope, so weigh the sealed letter before you rely on a single stamp.
The arithmetic starts with the paper. Ordinary 20 lb bond copy paper weighs 75 grams per square meter. A US Letter sheet is 8.5 × 11 inches, or about 0.0603 square meters, so each sheet weighs about 4.5 grams, roughly 0.16 ounce. Six sheets of paper alone come to about 0.96 ounce.
The envelope then adds its own weight, which varies with size, paper, and any window, so the paper figures below are a floor, not the final weight. That is why USPS’s rule of thumb, covered above, is about four sheets per 1-ounce stamp rather than six. Once the sealed letter goes over 1 ounce, it pays the 2-ounce price shown in the postage-by-weight table, and the 3.5-ounce letter limit and the nonmachinable surcharge rules described in this article still apply.
| Sheets of paper | Paper weight alone | Postage if the sealed letter stays in this step |
|---|---|---|
| 1–4 | 0.16–0.64 oz | $0.82 (up to 1 oz) |
| 5–6 | 0.80–0.96 oz | $0.82 if the envelope keeps it at 1 oz or less; otherwise $1.11 |
| 7–12 | 1.12–1.91 oz | $1.11 (up to 2 oz) |
| 13–18 | 2.07–2.87 oz | $1.40 (up to 3 oz) |
| 19–21 | 3.03–3.35 oz | $1.69 (up to 3.5 oz), if the envelope keeps it within 3.5 oz |
Envelopes that cost extra: the $0.49 surcharge
USPS sorts letters on high-speed machines. A letter that can’t run through them pays a $0.49 nonmachinable surcharge on top of the weight-based price, effective July 12, 2026. A 1-ounce square wedding invitation therefore costs $1.31, and USPS sells stamps for square, oversized, or unusual envelopes starting at that price.
Domestic Mail Manual section 101.1.2 lists the characteristics that make a letter nonmachinable. One is enough to trigger the surcharge:
- Its length divided by its height is less than 1.3 or more than 2.5, which includes square envelopes.
- It is polybagged, wrapped in plastic, or has an outside surface that is not paper. Paper envelopes with windows are fine.
- It has clasps, strings, buttons, or similar closures.
- It contains pens, keys, coins, or similar items that make it unevenly thick.
- It is too rigid to bend easily.
- It is thinner than 0.009 inch while longer than 6 inches or taller than 4.25 inches.
- The delivery address runs parallel to the short side, as on a vertical envelope.
- It is a self-mailer or booklet that isn’t prepared to the USPS standards for those formats.
Large envelopes and heavier mail
A letter-size piece can be no larger than 11.5 inches long, 6.125 inches high, and 0.25 inch thick, and it can weigh no more than 3.5 ounces. If you want to mail letter-size paper flat without folding it, you need a large envelope, which USPS calls a flat. Flats can be up to 15 × 12 inches and 0.75 inch thick, must bend, must be evenly thick, and can weigh up to 13 ounces as First-Class Mail.
A large envelope that is rigid, not rectangular, or lumpy pays package prices instead. Stamped mail that weighs more than 10 ounces or is thicker than half an inch cannot go in a collection box; hand it to an employee at a Post Office.
| Weight not over | Postage | Weight not over | Postage |
|---|---|---|---|
| 1 oz | $1.69 | 8 oz | $3.72 |
| 2 oz | $1.98 | 9 oz | $4.02 |
| 3 oz | $2.27 | 10 oz | $4.32 |
| 4 oz | $2.56 | 11 oz | $4.62 |
| 5 oz | $2.85 | 12 oz | $4.93 |
| 6 oz | $3.14 | 13 oz | $5.24 |
| 7 oz | $3.43 | Over 13 oz | Use a package service |
What’s the cheapest way to mail a letter?
If you already have the letter printed, an envelope, and a Forever stamp, mailing it yourself is the cheapest option: $0.82 for a standard 1-ounce letter. Nothing else beats the stamp price for one ordinary letter.
An online letter service costs more because it does more than pay postage. IRIS prints a finished PDF, places it in an envelope, addresses it, and mails it by USPS First-Class Mail to a US address. A one-page black-and-white letter costs $3.20 in total: a $3.00 service-and-postage fee plus $0.20 per black-and-white page, or $0.40 per color page. The quote depends on page count and options, so you don’t weigh anything or buy extra stamps for a longer letter.
That trade-off makes sense when you don’t have a printer or stamps, or you can’t easily get to a mailbox. IRIS mails individual letters to US addresses only. It doesn’t sell stamps, mail internationally, or handle mailing lists. Letters must be US Letter-size PDFs of up to 60 single-sided or 120 double-sided pages.
| Option | What you pay | What it covers |
|---|---|---|
| Forever stamp on a letter you print yourself | $0.82 for up to 1 oz | Postage only; you supply printing, paper, envelope, and the trip to a mailbox |
| Metered postage (businesses with a postage meter) | $0.78 for up to 1 oz | Postage only; requires a postage meter account |
| IRIS online letter, one black-and-white page | $3.20 total | Printing, envelope, addressing, and First-Class postage to a US address |
| IRIS online letter, each added page | +$0.20 black-and-white or +$0.40 color | Printing of the extra page; no separate weight charge |
Before you mail it
Write the return address in the top-left corner and the delivery address in the bottom center, and include the ZIP+4 code when you know it. If the date matters, ask a retail associate at a Post Office counter to hand-cancel the letter; USPS does that for free and the letter gets that day’s postmark.
Sending to another country costs more: a 1-ounce international letter is $1.75 from July 12, 2026. If you need proof that the letter was sent or delivered, postage alone won’t give you that record; compare Certified Mail and a Certificate of Mailing first.
Sources & further reading
Product details checked against the IRIS API contract when this article was published. Platform references can change; consult the linked documentation when implementing.
- USPS Notice 123, Price List effective July 12, 2026 (Postal Explorer)
- USPS newsroom, U.S. Postal Service Recommends New Prices for July (April 9, 2026)
- USPS, How to Send a Letter or Postcard
- USPS, First-Class Mail and postage
- USPS Domestic Mail Manual 101, Physical Standards
- USPS Notice 123, Price List effective October 4, 2026 (Postal Explorer)
Published by IRIS Postal Forms, operated by Great Lakes Computing Office LLC. Send a correction.