It is possible to look up a postal code using the Look Up a ZIP Code button on the website of the U.S. Postal Service, www.usps.com. The button is located on the left side of the page.
The U.S. Postal Service's website allows users to look up ZIP codes by address. It also allows users to look up all cities covered by a particular ZIP code. Another option for looking up ZIP codes is to use Google Maps. Entering an address, city and state into Google Maps brings up the ZIP code along with a map of the location in question.
For international addresses, if the country is known, postal codes or their corresponding cities can be found using the web site of that country's postal service. If neither the address or country is known, the postal code can be entered into a postal code search such as GeoNames, or, in some cases, the country can be determined based on the format of the postal code.