
ZIP+4 Codes are 4-digit codes added to traditional ZIP Codes that provide faster routing. The last 4 digits of the ZIP Code represent delivery route segments within delivery areas and generally consist of 10-20 mailboxes. For example, a ZIP+4 could indicate floor #16 in a high-rise, a street's north-facing homes, or a large business.
ZIP+4 Codes indicate small geographic areas. By adding a ZIP+4 to what you mail, the USPS instantly knows the date, time, and carrier that will place your letter in the mailbox. The USPS will also immediately knows every truck, airplane, and facility they'll use along the way.
That's how ZIP plus 4 codes help prevent misdelivered, lost, delayed, and returned mail. Including those last 4 digits can reduce delivery time by as much as 2 days!
Full 9-Digit ZIP Code Lookup
USPS ZIP+4 Code lookups are a cinch with the right tools, and Smarty provides easy-to-use options for single ZIP+4 Code lookups, looking up ZIP+4 Codes in bulk (up to millions at a time), and ZIP+4 Code lookup via API.
Single ZIP+4 Code Lookup | Bulk ZIP+ 4 Code Lookup | Zip+4 Code Lookup API |
---|---|---|
Look Up Now | Look Up Now | Look Up Now |
In this article; we'll cover:
- How to Find My ZIP+4 Code Extension?
- What ZIP+4 Codes Are.
- Full, 9-Digit ZIP Code Benefit
- How ZIP Codes Became 9-Digit-ZIP Codes
- ZIP+4 Code Database
- What Is My Full ZIP Code?
How to Find My ZIP+4 Code Extension
Quickly find the last 4 digits of ZIP Codes for almost any address in the United States by watching this video.
What ZIP+4 Codes Are

ZIP+4 Codes are 4-digit codes appended to the original 5-digit USPS ZIP Codes. Using the full ZIP Code with the extra 4 digits when mailing via the USPS ensures the fastest, most accurate mailing possible.
ZIP+4 Codes are also frequently referred to "Plus-Four Codes", "ZIP Code Extensions", "9-digit ZIP Codes", "Full ZIP Codes", or simply "Extended ZIP Codes". No matter what name you use, ZIP plus 4 codes aid the USPS in sorting and distributing mail effectively.
ZIP plus 4 lookup tools don't just find the full ZIP Code. The +4 shows after the address standardization and validation process confirm the address is mailable.
These codes indicate a specific delivery route, meaning the actual path the mail truck would travel in a single drop-off. Usually, this comprises ten to twenty homes or locations. The USPS also assigns ZIP+4 Codes to PO Boxes. Typically, each PO Box gets its own +4 Code, which often matches the box number.
The extra 4 digits on ZIP Codes identify segments of fluid postal delivery routes. They're not permanent lines, so those last 4 digits on 9-digit ZIP Codes can change regularly. Five-digit ZIP Codes also change, but they do so infrequently; it's less likely that you will live in a ZIP Code when it changes. Not so for the last 4 digits of zip codes.
The +4 on a ZIP Code can change as frequently as every month. Quantity of postal employees, new construction, remapping delivery areas, etc., are just a few things that cause ZIP+4 Code changes.
Full, 9-Digit ZIP Code Benefits

Here are a few benefits of looking up ZIP+4 Codes/9-digit ZIP Codes as a part of your address data management or shipping processes.
- Faster Shipping - Each ZIP+4 Code represents segments of delivery routes that are usually within a single block of the desired delivery point. That simple 9-digit number makes routing more efficient since the USPS knows which mail person will put the letter in the mailbox. Completing ZIP+4s on your mail can speed up processing and delivery, sometimes by as many as two days.
- Reduce Lost Mail & Misdeliveries - More efficient routing also means fewer opportunities for mistakes along the way.
- Less Returned Mail - Obtaining ZIP+4 Codes requires validation; that means the address is a valid delivery point. It also means the address information is standardized to the USPS address format. Mail delivery is more reliable with a valid, standardized address with ZIP4 Code since the address data is clearly understood.
- Save Money with Bulk Mailings - If you send at least 50 packages or more than 200-500 pieces of mail, you may be able to qualify for commercial mailing discounts. By adding ZIP+4 Codes, Delivery Point Barcodes, and sorting/bundling your mail, you can get discounts up to 5% to nearly 60% off the prices you'd pay at the post office.
- Cleaner Address Data - Addresses must be validated, standardized, and corrected before you get the ZIP+4 Code. So, you get much more than a pretty 9-digit ZIP Code; you get a clean, standard address. Clean, standard addresses are easy to sort and compare. Comparing a table of standardized, verified addresses allows you to identify duplicates, delete redundancies or merge records easily.
- Enriched Address Data - When you give Smarty an address and ask for the ZIP+4 Code, we give you the ZIP+4 Code along with the validated, standardized address. We also provide up to 45 data points about the address, including county information, lat/long coordinates, time zone, whether the address is residential or commercial, and more data that can be used for business intelligence and to understand your mail recipients better.
That's right. Your mail can show up faster, cheaper, and more reliably if you label things right, plus you get less returned mail. Bet you're scrambling to look up those full ZIP Codes now. Grab those extra 4 digits now.
How ZIP Codes Became 9-Digit-ZIP Codes

Fully understanding the last four digits of ZIP Codes requires knowing about 5-digit ZIP Codes too.
These are the codes you know. They look like this.
The Zone Improvement Plan (ZIP) was something the USPS came up with to make it easier to ship letters and packages across the country. ZIP helps divide the country into different "zones" according to the distribution of mail, which accelerates sorting and delivery.
On July 1, 1963, the Post Office Department launched the Zone Improvement Plan. At the same time, they introduced the world to Mr. ZIP or "Zippy." Zippy is the official ZIP Code mascot pictured on our ZIP Codes 101 page. They also released the ZIP Code jingle:
As the US population has increased and scattered since 1963, it's been necessary to expand the system to make room for everybody and their dog. That's where the "plus 4" part comes in. We're getting ahead of ourselves, so let's start with the basics.
If you're mailing a letter from Boston to Seattle, the mail carrier in Massachusetts doesn't care what the street address of the destination is. It's what you might call "outside his jurisdiction." He just needs to know which mail carrier to send it to so the appropriate mailperson can get it to the address.
A postal worker can only cover so much ground on a given day. And since the USPS has a standard of delivering in the rain, sleet, or snow, that rules out the possibility of doing the service of delivery in stages (some today, some tomorrow). That means any given post office only serves what it can reach in a day. ZIP Codes reflect that.
Typically, a ZIP Code ties to a post office; by that, we mean every one of the latter has one of the former. You might think of ZIP Codes as a mailing address for a particular post office. Some handle more than one ZIP Code, but a one-on-one game plan is a standard.
It's essential to note that ZIP Codes aren't "boundaries." They're a collection of delivery routes. They don't follow geographic or administrative boundary lines; they can cross city, county, and statelines. They follow where the delivery trucks go.
Some ZIP Codes are a bit different in function. Among them are "military" ZIP Codes, which include everythingfrom military bases (domestic or otherwise) to battleships at sea. Then there are "unique" ZIP Codes. Businesses and organizations sometimes get a dedicated ZIP Code that they don't have to share with anyone due to the volume of mail they send and receive.
These frequently benefit from bulk mailing discounts since the organization usually has a mail department that (1) presorts mail before giving it to the USPS and (2) distributes mail internally, so the USPS doesn't have to. Like standard ZIP Codes, "military" and "unique" ZIP Codes circumscribe their delivery area. For a more in-depth guide, visit our ZIP Codes page.
ZIP+4 Code Database
For many users, the best way to access the USPS ZIP+4 database is through a CASS Certified USPS address validation vendor. Like Smarty. Since the last four digits of ZIP Codes update frequently, even month-old data isn't reliable. Checking addresses regularly against the database will ensure your data remains clean.
The ZIP+4 Code database can be accessed free directly through the USPS site or the USPS address validation API. In our USPS APIs article, you will find a comprehensive list of uses and limitations of the USPS web-based tool and API.
What Is My Full ZIP Code?
If you need an answer to, "What is my ZIP Code with the extra 4 digits?" Just click one of the buttons at the top of the page, enter your address, and get your +4 code instantly. That was easy!
The quiz will include three things:
- ZIP+4 Codes indicate delivery routes.
- Using ZIP+4 Codes gets your mail there faster and more accurately.
- We at Smarty can get you those codes.
If you want to try it on a single address, you can now use our SingleAddress Verification Tool. Our blindingly fast US AddressVerification API provides the appropriate ZIP+4 Code for every address we process.
Or you could call us instead if you'd rather talk to an actual person. (We'd offer a fakeperson, but we don't have one of those on staff.) Either way, we can help you ZIP your address and ZIPit well.
FAQs
How many addresses are in a zip 4? ›
ZIP+4 Codes are 4-digit codes added to traditional ZIP Codes that provide faster routing. The last 4 digits of the ZIP Code represent delivery route segments within delivery areas and generally consist of 10-20 mailboxes.
Which states have 4 digit zip codes? ›ZIP Codes Beginning With | States / Territories |
---|---|
4 | Indiana, Kentucky, Michigan, Ohio |
5 | Iowa, Minnesota, Montana, North Dakota, South Dakota, Wisconsin |
6 | Illinois, Kansas, Missouri, Nebraska |
7 | Arkansas, Louisiana, Oklahoma, Texas |
Definition of zip code
1 : a number that identifies a particular postal delivery area in the U.S. 2 : the geographic area identified by a zip code. zip-code. verb.
In 1983, the U.S. Postal Service introduced an expanded ZIP Code system that it called ZIP+4, often called "plus-four codes", "add-on codes", or "add-ons".
How do I create a ZIP code? ›To create a personal Zip, a postal customer would go to a postal web site, authenticate who they are, much as they do today to sign up for Informed Delivery, and provide their current address and, optionally, email address. The system would provide them their own 11 (or 12) digit Personal Zip Code.
How do you write an address with a zip code? ›Addresses (ZIP code present)
USPS abbreviations are used for both the street address and state, and there is no punctuation in the lines for the street address or city, state and ZIP code. Write to Paul and Mary Moore, 1313 E Main St, Portage MI 49024-2001.
So what do the extra numbers mean? These last 4 digits represent specific delivery routes within delivery areas. This extra detail means an even more precise matching to a more granular level. It could represent a handful of houses on one side of a street, or even a single building that receives a high volume of mail.
Why are some ZIP Codes 4 digits? ›Your ZIP+4 is a basic five-digit code with four digits added as an extra identifier. It helps to identify a geographic segment within the five-digit delivery area, such as a city block, a group of apartments, an individual high-volume receiver of mail, or a post office box.
What is an example of a ZIP Code? ›Standard US ZIP codes
The standard ZIP code notation used by the United States Postal service uses five digits to identify a delivery area. An example of a standard US ZIP code is 90210.
It refers to the code in the post office number of the postal code system which is predominantly used in the India Post to segregate the mails. The Postal Index Number consists of six long digits.
What does ZIP mean in address? ›
A ZIP Code is a postal code used by the United States Postal Service (USPS). The ZIP code is the part of the address that designates delivery areas. It indicates the destination post office or delivery area to which a letter or parcel will be sent for final sorting for delivery.
How do I find the ZIP Code for my location? ›- Visit postcode.com.ng homepage.
- Click on the state you're located in.
- Select your local government.
- Search for your town.
The ZIP+4 code is used and assigned by the United States Postal Service (USPS) for routing purposes. The final 4 digits are not required for delivery of your mail and may change frequently. There have been several +4 digit changes as a result of the Marathon County Uniform Addressing Program.
What happens if I use the wrong ZIP Code? ›Usually what happens is a carrier or post master from the office where the package is sent will correct the zip code by looking at the address and even reach out to that particular post office to ensure the package is delivered to the correct address.
Whats a ZIP Code on a card? ›The zip code on a credit card is the security measure used to confirm that the card owner is using it. This code is anchored to the five-digit postal code of the billing address where you receive your card information.
Can I make my own ZIP code? ›You don't make a zip-code. If you live in a country that uses them, your zip-code is based on where you live.
How do I use zip files? ›Right-click on the file or folder.
Select “Compressed (zipped) folder”. To place multiple files into a zip folder, select all of the files while hitting the Ctrl button. Then, right-click on one of the files, move your cursor over the “Send to” option and select “Compressed (zipped) folder”.
123 Main Street, New York, NY 10030 is an example of an address. A formal speech or written communication.
How do you correctly write your address? ›- Always put the address and the postage on the same side of your mailpiece.
- On a letter, the address should be parallel to the longest side.
- All capital letters.
- No punctuation.
- At least 10-point type.
- One space between city and state.
- Two spaces between state and ZIP Code.
How To Say American Addresses - YouTube
What a ZIP Code looks like? ›
A United States postal code, for example, might be either five digits or five digits followed a hyphen (dash) and another four digits (12345-1234). If you are validating US postal codes, allow for both conditions. The following rule validates a field that can be five digits, five digits + dash + 4 digits, or blank.
How are Zipcodes determined? ›As of 1963, zip codes' numbers are determined by a few factors: the area, the regional postal facility and the local zone. The first number of the five-digit code signifies the region which the address is located in, a number that grows from the east coast to the west.
How many digits is a US ZIP Code? ›A 5-digit number that identifies a particular postal delivery area in the United States.
Is ZIP Code always 5 digits? ›ZIP & ZIP+4
United States ZIP codes are five numerical digits long. ZIP+4 codes, also known as add-on or plus-four codes, include four additional digits that identify a geographic segment within a ZIP code delivery area.
ANSWER: The two codes are essentially the same in their purpose, but the term Zip code is mainly used in the USA; Postal Code is commonly used in other countries.
What is a 5 number ZIP Code? ›The term ZIP stands for Zone Improvement Plan. The basic 5-digit format was first introduced in 1963 and later extended to add an additional 4 digits after a dash to form a ZIP+4 code. The additional 4 digits help USPS more precisely group mail for delivery.
Is ZIP Code and PIN code same? ›PIN code stands for Postal Index Number code. Also known as Zip code or area postal code, Pin code is the post office numbering code system used by the postal service of India, India Post.
What is my 6 digit PIN code? ›...
PINCODE.
First Digit | Region | States Covered |
---|---|---|
6 | Southern | Kerala and Tamil Nadu |
7 | Eastern | West Bengal, Orissa and North Eastern |
8 | Eastern | Bihar and Jharkand |
9 | APS | Army Postal Service |
A ZIP code (Zone Improvement Plan code) is a 4-digit number added to your address for the sake of speeding up the process and ensuring the accuracy of delivery services. It is commonly used by PhilPost (Philippine Postal Corporation) and other mail services in delivering postal mail.
How do you pronounce zip code numbers? ›How To Say Zip Code - YouTube
How do you pin code? ›
- The first digit indicates: northern region = 1.
- The first 2 digits indicate: postal circle Delhi = 11.
- The third digit indicates: sorting district = 0.
- The last 3 digits indicate: the specific post office (Connaught Place) = 001.
Zip Code | City | County |
---|---|---|
90230 | Culver City | Los Angeles County |
90231 | Culver City | Los Angeles County |
90232 | Culver City | Los Angeles County |
90233 | Culver City | Los Angeles County |
So what do the extra numbers mean? These last 4 digits represent specific delivery routes within delivery areas. This extra detail means an even more precise matching to a more granular level. It could represent a handful of houses on one side of a street, or even a single building that receives a high volume of mail.
How do you read a zip code? ›What each number means. The first digit designates a broad area, which ranges from zero for the Northeast to nine for the far West. The two following digits are the code of a central post office facility in that region. The last two digits designate small post offices or postal zones.
How often do zip codes change? ›The USPS updates their zip codes quarterly.
What is a valid US zip code? ›The current postal codes in the United States range from 00001 – 99950.
What happens if I use the wrong zip code? ›Usually what happens is a carrier or post master from the office where the package is sent will correct the zip code by looking at the address and even reach out to that particular post office to ensure the package is delivered to the correct address.
What is the plus 4 on a ZIP code? ›Your ZIP+4 is a basic five-digit code with four digits added as an extra identifier. It helps to identify a geographic segment within the five-digit delivery area, such as a city block, a group of apartments, an individual high-volume receiver of mail, or a post office box.
What happens if you forgot to put the zip code on a letter? ›A letter without a ZIP code may not reach its intended destination. That is because of the way addresses are read by automated postal systems. Rules that are taken for granted when people send mail are actually unusually strict to increase post office efficiency. Processing machines read addresses from the bottom up.
What is an example of a ZIP Code? ›Standard US ZIP codes
The standard ZIP code notation used by the United States Postal service uses five digits to identify a delivery area. An example of a standard US ZIP code is 90210.
How does a ZIP file work? ›
ZIP files work in much the same way as a standard folder on your computer. They contain data and files together in one place. But with zipped files, the contents are compressed, which reduces the amount of data used by your computer. Another way to describe ZIP files is as an archive.
What is a ZIP 4 code and how is it different from a 5 digit ZIP Code? ›A ZIP+4 code uses the basic five-digit code plus four additional digits to identify a geographic segment within the five-digit delivery area, such as a city block, a group of apartments, an individual high-volume receiver of mail, a post office box, or a specific delivery route — meaning the actual path the mail truck ...
Do ZIP Codes get deleted? ›Are zip codes ever deleted from use? Over 1,000 ZIP codes have been decomissioned as post offices close or the needs of the United States Postal Service change.
Is postal code the same as ZIP Code? ›Zip code refers to a type of postal code and is used primarily in the United States and the Philippines. The postal code, however, is typically utilized by the rest of the countries scattered throughout the world.
What is a unique ZIP Code? ›What are unique ZIP codes? In short, unique ZIP codes are high volume mail receivers that receive mail at one location and then distribute the mail internally. Unique ZIP codes generally are used by large organizations, government buildings, universities or large medical facilities.
How do I find the ZIP Code for my location? ›- Visit postcode.com.ng homepage.
- Click on the state you're located in.
- Select your local government.
- Search for your town.
The zip code on a credit card is the security measure used to confirm that the card owner is using it. This code is anchored to the five-digit postal code of the billing address where you receive your card information.
What is a ZIP Code on a credit card? ›A credit card postal code is simply the primary cardholder's postal code, part of their mailing address. Some merchants may ask you to enter your postal code to help verify your identity before processing a credit card transaction.