Spread Out Zip Code Resolution For Free

A 5-Digit ZIP code represents a USPS delivery area. A 9-Digit ZIP code, also known as a ZIP+4 code or an extended ZIP code, includes the same information as the 5-Digit ZIP code, plus additional information about a specific delivery route within the delivery area.

This is because ZIP code boundaries are based on mail routes and delivery points rather than geographic factors. The U.S. Post Office Department, predecessor to USPS, developed a zoning address system in 1943 as a way to make sorting and delivery of mail easier.

ZIP Codes are numbered with the first digit representing a certain group of U.S. states, the second and third digits together representing a region in that group (or perhaps a large city) and the fourth and fifth digits representing a group of delivery addresses within that region.

So what do the extra numbers mean? These last 4 digits represent specific delivery routes within delivery areas. This extra detail means an even more precise matching to a more granular level. It could represent a handful of houses on one side of a street, or even a single building that receives a high volume of mail.

Yes, when using a ZIP+4 ZIP Code, the number must consist of five digits, a hyphen (or dash), and four digits. Improperly labeled mailpieces may progress slower through the mail system and may be returned to sender if the United States Postal Service® is unable to deliver the item.

A United States postal code, for example, might be either five digits or five digits followed a hyphen (dash) and another four digits (12345-1234).

The standard ZIP code notation used by the United States Postal service uses five digits to identify a delivery area. An example of a standard US ZIP code is 90210.