How can you find zip codes that include the extra four digits?

As of 2015, you can find the nine-digit ZIP code of an address on the United States Postal Service's website, USPS.com. UnitedStatesZIPCodes.org also features a nine-digit ZIP code look up tool.

To find the nine-digit ZIP code for an address, navigate to USPS.com and click on Look Up a ZIP Code. On the next page, enter the street address and city, select the state and click Find.

To find the nine-digit ZIP code on UnitedZIPCodes.org, enter the street address, city and state, then click Search. The nine-digit ZIP code and a regional map of the area is displayed. Other statistics and demographics for the ZIP code are also included at the bottom of the results page.