A standard one-ounce letter sent by First-Class Mail costs $0.78 as of January 2026, and First-Class Mail rates climb from there based on weight, shape, and whether the piece can run through automated sorting equipment. Delivery takes one to five business days within the United States.
What You Pay by Shape and Weight
The Postal Service sets three price tracks under First-Class Mail: postcards, letters, and large envelopes (also called flats). The retail rates effective January 18, 2026 are:
- Postcard: $0.61
- Letter, first ounce: $0.78
- Each additional ounce on a letter: $0.29 (a two-ounce letter runs $1.07; three ounces runs $1.36)
- Large envelope, first ounce: $1.63, scaling to $5.04 at 13 ounces
These are published in Notice 123, the USPS official price list.1United States Postal Service. Notice 123 – January 2026 Price Change
A Forever Stamp covers one ounce of First-Class letter mail at whatever the current rate is. Because it’s non-denominated, one you bought years ago at a lower price still works today with no extra postage.2United States Postal Service. Postage Stamps – The Basics
USPS has proposed raising the one-ounce letter rate to $0.82 in July 2026, subject to regulatory approval.3United States Postal Service. USPS Recommends New Prices for July
When You Pay Extra: The Non-Machinable Surcharge
A letter that can’t run through USPS sorting equipment carries a $0.49 surcharge on top of regular postage.1United States Postal Service. Notice 123 – January 2026 Price Change A one-ounce square greeting card actually costs $1.27 to mail, not $0.78.
A letter is non-machinable if any of the following applies:4USPS Postal Explorer. 201 Quick Service Guide
- It’s square, or otherwise has an aspect ratio outside the 1.3 to 2.5 range
- It has clasps, strings, buttons, or similar closures
- It contains rigid objects like pens, pencils, or keys that create uneven thickness
- The envelope itself is too stiff to flex through the machinery
- The address runs parallel to the shorter side of the envelope
- The envelope is made of material other than paper (standard window envelopes are fine)
Wedding invitations and lumpy holiday cards are the classic offenders. Budget the extra $0.49 per piece.
Size Rules That Decide Your Rate
How your mail is classified determines how much you pay. The Domestic Mail Manual, incorporated by federal regulation at 39 CFR 111.1, sets the standards.5eCFR. 39 CFR 111.1 – Incorporation by Reference, Mailing Standards of the United States Postal Service, Domestic Mail Manual
To qualify as a letter, a piece must meet all of these:
- Weight: 3.5 ounces or less
- Height: 3.5 to 6.125 inches
- Length: 5 to 11.5 inches
- Thickness: 0.007 inch to 0.25 inch
- Aspect ratio (length divided by height): between 1.3 and 2.5
Anything larger than those dimensions but under three-quarters of an inch thick is a large envelope. Large envelopes can weigh up to 13 ounces. Above 13 ounces, the piece no longer qualifies for First-Class Mail and has to move to Priority Mail or USPS Ground Advantage.6USPS Postal Explorer. 100 Retail Mail Letters, Cards, Flats, and Parcels
How Long Delivery Takes
First-Class Mail is delivered in one to five business days depending on distance.7United States Postal Service. First-Class Mail Local mail within the same metro area often arrives in a day or two. Cross-country and rural delivery generally takes the full window. These are service targets, not guarantees; weather and seasonal volume can push delivery later. For anything time-sensitive, like a legal notice or a bill payment, build in a buffer.
Adding Tracking or Proof of Delivery
A standard First-Class letter has no tracking. Drop it in the mailbox and there’s no way to confirm arrival unless you buy an extra service.8United States Postal Service. USPS Tracking – The Basics This surprises people sending checks, contracts, or signed documents.
The main add-ons, purchased at the counter or online:
- Certified Mail, $5.30. Gives you a mailing receipt and electronic verification of delivery or attempted delivery. Standard choice for legal notices, lease terminations, and demand letters.9United States Postal Service. Certified Mail – The Basics
- Return Receipt: $4.40 for a hard-copy signature card, $2.82 for an electronic version. Proves a specific person received the item.10United States Postal Service. Notice 123 Price List
- Registered Mail: the highest-security option, with each handoff logged in a documented chain of custody. Fees start at $19.70 with no declared value and rise to $38.00 for items valued up to $5,000.1United States Postal Service. Notice 123 – January 2026 Price Change
- Insurance: covers loss or damage up to the declared value, priced by coverage amount.
These stack on top of postage. A certified letter with electronic return receipt runs $0.78 plus $5.30 plus $2.82, or $8.90 before anything else.
If Your Letter Can’t Be Delivered
First-Class Mail comes back to you for free when it can’t be delivered or forwarded, provided you included a return address.11USPS Postal Explorer. 507 Mailer Services Lower classes like marketing mail don’t get returned; they’re discarded. Without a return address, the piece heads to a USPS mail recovery center where staff open it to try to identify sender or recipient. Always print a return address in the upper left.
If the recipient filed a change-of-address order, USPS forwards First-Class Mail at no charge for 12 months. After that window, the piece comes back to you with the new address attached.
Formatting the Address
Automated sorting reads addresses best when they follow a predictable format:12United States Postal Service. Addressing Mailpieces
- Center the delivery address on the envelope, in all capital letters with no punctuation, 10- to 14-point font
- Put apartment or suite numbers on the same line as the street address, after the street name
- Use the two-letter state code
- Include the five-digit ZIP, or ZIP+4 when you have it
- Return address in the upper left, postage in the upper right
Commercial Rates for Bulk Senders
Businesses mailing at least 500 pieces at a time can access commercial First-Class Mail prices, which are lower per piece than retail.13USPS Postal Explorer. First-Class Mail Prices and Eligibility There’s no single flat discount; the rates break out by preparation category (automation-compatible, presorted, or non-automation machinable) and each has its own price. Businesses need a USPS mailing permit and pay an annual presort fee at each entry post office. Postage meters and permit imprints are the usual payment methods since sticking stamps on hundreds of pieces isn’t practical.2United States Postal Service. Postage Stamps – The Basics USPS Connect Local Mail is the exception to the 500-piece minimum and has no volume floor.
What You Can’t Send
USPS prohibits hazardous materials including explosives, flammable liquids, corrosives, radioactive material, and toxic or infectious substances. Restricted items subject to special rules or outright bans include firearms, knives, controlled substances, alcohol, and cigarettes.14USPS Postal Explorer. Mailability
Lithium batteries come up often because they live in nearly every electronic device. Batteries installed in or packed with their device can go by air or ground. Standalone lithium batteries shipped without equipment are ground-only, with per-cell limits (1.0 gram of lithium content for lithium metal, 20 watt-hours for lithium-ion) and a package cap of eight cells or two batteries. Packages need a DOT-approved lithium battery handling mark on the address side.15USPS Postal Explorer. Publication 52 – Appendix C – USPS Packaging Instruction 9D Perishables like fresh food, live animals, and plants have their own rules and generally don’t fit the one-to-five-day First-Class window. Publication 52 is the reference when you’re unsure.
International Letters
First-Class Mail International covers letters and large envelopes going to other countries. Letters keep the 3.5-ounce domestic ceiling; large envelopes can go up to just under 16 ounces. Postage is higher than domestic and varies by destination tier, so Canada costs less than Australia. Customs declaration forms may be required even for documents, and there’s no specific day-count guarantee on delivery.16USPS Postal Explorer. International Mail Manual