How long does it take for letter delivery within the same city?

The USPS delivers First-Class letters within one to three days, though the speed is not guaranteed. In practice, distance plays a role in the speed of First-Class delivery, with letters mailed within the same city often delivered the day after they are mailed.

In 2009, the New York Daily News conducted an informal experiment and noted that a letter mailed from Manhattan to Brooklyn arrived one day later regardless of the class of service. The U.S. Postal Service offers Priority Mail and Priority Mail Express services for customers who are willing to pay more for potentially quicker delivery. Customers who need a money-back guarantee that an item is delivered by a certain date must choose the premium Priority Mail Express service.