How Many Ounces Does a Standard Letter Weigh?

Standard mail rates appeal to businesses that want to maintain low marketing and advertising costs. The United States Postal Service requires customers to mail a minimum of 200 pieces or 50 pounds at a time to qualify for standard mail rates. Letters, packages, large and flat envelopes vary in shipping price. Additional insurance and USPS services such as USPS tracking and return receipts cost extra. Domestic addresses, not international addresses, qualify for standard mail rates.