First-Class Mail service is an affordable and easy way to send envelopes and postcards. 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. To send packages, see USPS Ground Advantage service.

First-Class Mail service is an affordable and easy way to send envelopes and postcards. 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. To send packages, see USPS Ground Advantage service. Features & Pricing: - Mail delivered in 1–5 days - Our best-priced service for items up to 13 oz - One price for up to 3.5 ounces with commercially priced letters and cards - Prices based on shape and weight Postmarking & Proof of Mailing: If you want to ensure that your mail receives a postmark on the day you mail it, ask a retail associate at a Post Office retail counter to hand-cancel it for free. To get an official record that you sent an item on a specific date, you can pay an extra service fee for a Certificate of Mailing. Proof of Delivery: First-Class Mail items are eligible for Delivery Confirmation services such as Certified Mail. Standard Letter & Postcard Sizes: - Letters: Standard-sized, rectangular envelope stamps start at $0.82. Square, oversized, or unusually shaped envelope stamps start at $1.31. - Postcards: Standard-sized, rectangular postcard stamps start at $0.65. Oversized postcards need letter stamps, which start at $0.82. - Large Envelopes: Large envelopes (flats) start at $1.69. Weight, Size, & Shape Requirements: Maximum weight for First-Class Mail letters is 3.5 oz; for large First-Class Mail envelopes, the maximum weight is 13 oz. All postcards and envelopes (or flats) must be rectangular, otherwise an additional charge may apply. Additional Charges for Irregular Mailpieces & Envelopes: - Nonmachinable Envelopes: Unusually shaped mail, like square or vertical envelopes, lumpy envelopes, rigid envelopes, and mail with clasps, string, or buttons, must be hand-canceled and are charged a nonmachinable surcharge even if they weigh less than 1 oz. - Large Mailpieces: Letters that exceed the First-Class standard envelope maximum length, height, or thickness are charged large envelope (flat) prices. - Large Envelopes (flats) Treated as Small Packages: Large First-Class envelopes (flats) that exceed maximum dimensions or are rigid, non-rectangular, or not uniformly thick are charged package prices and shipped with USPS Ground Advantage. For Businesses: First-Class Mail commercial pricing is available for presorted letters and flats with a minimum quantity of 500 mailpieces. Automation discounts may also apply. One Price Up to 3.5 Ounces: Pay one price for up to 3.5 oz for First-Class Mail presort and automation compatible letters and cards.