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USPS ZIP+4 Lookup Tool (Free)

Enter a full address to get the correct 9-digit ZIP+4 code and USPS-standardized address format using USPS address data.

Look Up ZIP+4 Code

What is ZIP+4?

ZIP+4 is the Post Office's way of narrowing down where a piece of mail should go. Those extra four digits can help identify details like what side of the street your house or building is on, or even which building you are in.

That helps with sorting and can help get your mail to you, or to your destination, faster. ZIP+4 is not required for most mail, but using it can make delivery more accurate.

Why we built this tool

We could not find a reliable way to quickly look up ZIP+4 codes accurately, so we made this tool to help people quickly validate the ZIP+4 for an address.

If you use our online mail service, we automatically apply ZIP+4 as part of preparing your letter.

Why ZIP+4 lookup might fail

ZIP+4 lookup usually depends on having the address exactly right. If the address is for an apartment building, office building, or another multi-unit location, USPS may need the apartment, suite, or unit number before it can confirm the exact delivery point.

Small spelling issues can also block a clean match. A street name, city, or ZIP code that is slightly off may prevent the lookup from finding the right record.

New construction, renamed streets, and recent address changes can also take time to show up. If one search does not work, try adding more locality details, such as the city, state, and 5-digit ZIP together.

Frequently Asked Questions

What is a ZIP+4 code?
A ZIP+4 code is the standard five-digit ZIP Code plus four digits that identify a more specific delivery segment, such as a city block, building, floor, or high-volume recipient.
Do I need a ZIP+4 code to mail a letter?
Usually not. A correct five-digit ZIP Code is enough for most mail, but adding the ZIP+4 can help USPS sort the piece more precisely and reduce address ambiguity.
Where does this ZIP+4 data come from?
The lookup uses USPS address data to standardize the address and return the ZIP+4 associated with that deliverable address.
Why didn't I get a ZIP+4 code?
USPS couldn't fully confirm the exact address. This usually happens when there's a typo, missing unit number, or the address is too new to be in the database. Double-check the spelling, add any missing apartment/suite numbers, and try again.