First-Class Mail® service is an affordable and easy way to send envelopes and postcards. First-Class Mail Forever® stamps cost $0.78 (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 $0.78 (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 Prices: - Letters (standard-sized, rectangular): $0.78 - Letters (square, oversized, or unusually shaped): $1.27 - Postcards (standard-sized, rectangular): $0.61 - Postcards (oversized): $0.78 - Large Envelopes (flats): $1.63 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 must be rectangular, otherwise an additional charge may apply. Additional Charges for Irregular Mailpieces & Envelopes: Unusually shaped mail, including 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. Letters exceeding standard envelope maximum dimensions are charged large envelope prices. For Businesses: USPS offers commercial pricing for presorted letters and flats with a minimum quantity of 500 mailpieces. Automation discounts may also apply. First-Class Mail is targetable, trackable with certain extra services, and measurable, offering address correction and forwarding services.