A ZIP+4 code is the five-digit ZIP plus a four-digit extension that points to a smaller delivery segment, such as one side of a street, a floor of a building or a range of PO Boxes. Because the extra four digits depend on the exact address, the only reliable ZIP+4 lookup is an address lookup.
Find your 9-digit ZIP code
The official USPS lookup returns the full nine-digit ZIP code for any deliverable U.S. address. Enter the street address, apartment or suite number, city and state.
Opens USPS in a new tab. This site does not collect, store or verify your street address.
Five digits + four more
02108−1234
Format illustration only. The last four digits above are not a verified address match.
“9-digit ZIP,” “ZIP plus 4,” “full ZIP code,” “extended ZIP code” and “ZIP+4” all mean the same thing. The four-digit extension on its own is never a complete ZIP code.
How the four extra digits work
USPS introduced ZIP+4 in 1983; the extra numbers let mail be sorted to a specific street, and in 1991 two more digits were added so mail could be sorted to a single delivery point (USPS Postal Facts ↗). Within the extension, the first two digits identify a delivery sector and the last two a delivery segment. USPS maintains the codes as routes change, so a ZIP+4 you noted years ago may no longer be current.
Do you need ZIP+4?
Situation
Is ZIP+4 required?
Everyday letters and parcels
No. Five digits are enough; ZIP+4 can slightly speed up sorting.
Bulk or presorted business mail
Usually. Automation prices depend on standardized addresses with ZIP+4 and barcodes.
Forms with a nine-digit field
If the form requires it. Use the USPS lookup rather than guessing.
A ZIP+4 cannot be derived from a five-digit ZIP, a city or map coordinates. Any tool that shows one without your full address is guessing. This site never fills in the last four digits; for everything that does not depend on the street address, use the five-digit ZIP code lookup.
Already know the five-digit ZIP?
Open its page to see the recorded place, county association, map reference point and nearby ZIP codes.
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