How many stamps for 6.7 oz?

The number of stamps needed for a 6.7 oz letter depends on the mailing service you use. For example, as of 2023, a standard First-Class Mail letter can weigh up to 1 oz for a single stamp, with additional ounces requiring extra postage. Typically, each additional ounce costs extra, so you would need to check the current USPS rates. For a 6.7 oz letter, you would likely need a combination of 1-ounce stamps plus additional ounces' worth of postage, often totaling around 3 or 4 stamps.