cost to mail 1st class letter varies depending on the size, weight, and destination of the letter. In the United States, the U.S. Postal Service (USPS) offers First-Class Mail for standard letters, which is one of the most affordable mailing options. As of recent updates, the cost of sending a standard 1-ounce letter via First-Class Mail starts at a set rate, with additional fees for heavier letters or special services such as tracking or insurance. First-Class Mail is popular for personal correspondence, business letters, and small documents due to its low cost and fast delivery, typically taking 1 to 3 business days for domestic shipments. The USPS also offers price calculators on their website to help customers determine the exact cost of sending mail based on its weight and destination.