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9-digit ZIP code finder

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

USPS requires a full street address plus either city & state or a 5-digit ZIP code.

What is ZIP+4?

ZIP+4 adds four digits to a standard 5-digit ZIP code. Those extra digits help USPS narrow a delivery route to a more precise segment, building, floor, or high-volume delivery point.

You can usually mail with only the 5-digit ZIP, but a confirmed ZIP+4 can improve sorting accuracy and reduce avoidable delivery issues.

Why ZIP+4 lookup might fail

  • Missing apartment or unit: multi-unit buildings often need the secondary address line before USPS can confirm the exact delivery point.
  • Street spelling or city mismatch: small typos can prevent a clean USPS match.
  • New or changed addresses: very new construction, renamed streets, or recent address changes may not return a ZIP+4 immediately.
  • Not enough locality data: try adding both city/state and the 5-digit ZIP when one input alone does not match.

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Frequently Asked Questions

What is a ZIP+4 code?
A ZIP+4 code is a 9-digit postal code that adds four digits to the standard 5-digit ZIP code. The extra four digits narrow down the delivery point more precisely—often to a specific street segment, building, or even individual floor.
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.
Do I need ZIP+4 to mail a letter?
No, the 5-digit ZIP code is sufficient for USPS delivery. However, including the ZIP+4 improves sorting accuracy, speeds up delivery, and reduces the chance of your mail being returned or misdelivered.
Where does the ZIP+4 data come from?
This lookup tool checks USPS address data through The Letter Pilot and returns the standardized address details available for the address entered.

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