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 - 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 Standard Pricing: Letters: Standard-sized, rectangular envelope stamps start at $0.78. Square, oversized, or unusually shaped envelope stamps start at $1.27. Postcards: Standard-sized, rectangular postcard stamps start at $0.61. Oversized postcards need letter stamps, which start at $0.78. Large Envelopes: Large envelopes (flats) start at $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. Postmarking & Proof of Mailing: Hand-cancellation is available free at Post Office retail counters. Certificate of Mailing is available for an extra service fee. First-Class Mail items are eligible for Delivery Confirmation and Certified Mail services. For Businesses: First-Class Mail commercial pricing is available for presorted letters and flats with a minimum quantity of 500 mailpieces. Automation discounts may apply. The service is targetable, trackable with certain extra services, and measurable.