How to Find the 4 Digit Zip Code Extension for a Specific Address

The Postal Service created the four-digit extension to ZIP codes to assist in mail sorting.

The United States Post Office created ZIP codes in 1963 to help it handle mail more efficiently. The numbers in a ZIP code refer to a geographical area, regional area and specific Post Office. The four-digit extension was added in 1983, and these numbers sort the mail to specific streets or large apartment buildings.

Instructions

1. Direct your Internet browser to the USPS ZIP code finder, ZIPcodes.com or the ZIP code finder at Semaphore Corp. Links to these sites are listed in the Resources section.

2. Enter the street address, city and state code for the location the four-digit extension is needed for.

3. Press Enter or click the Submit or Find button located below the address entry form. The full USPS standard address will display, with the four-digit extension following the dash at the end of the five-digit ZIP code.

Tips & Warnings

• Enter the full address into the address search. An incomplete address will yield multiple responses.

References

• USPS: Decoding ZIP Codes

Resources

• USPS: ZIP Code Lookup
• ZIP-Codes: ZIP Code Finder
• Semaphore Corp.: National Address and ZIP+4 Finder