The U.S. Postal Service delivers first-class letter correspondence in one to three business days, but it does not explicitly guarantee its arrival in that time. The exact time needed varies depending on the distance between the origin and destination as well as the drop-off time.
Parcel delivery takes longer than mail correspondence, as USPS Parcel Post and Media Mail standard rates are quoted at two to eight business days. The U.S. Postal Service offers expedited services for an additional fee and is capable of delivering both parcels and letters overnight via Express Mail. Delivery involving origins or destinations outside the contiguous United States may take longer and is dependent on transportation availability.