What Is My Full ZIP Code? ZIP+4 and the Extra 4 Digits

Your full ZIP code is your 5-digit ZIP code plus 4 more digits after a hyphen, like 22162-1010. The US Postal Service (USPS) calls it ZIP+4. The 4 extra digits point to a small part of your ZIP code area, such as one side of your street or your building. Most forms only need the first 5 digits.

Table of contents

• What Is ZIP+4?
• What Do the Extra 4 Digits Mean?
• Do You Need the Extra 4 Digits?
• How to Find Your Full ZIP Code
• Common Mistakes With ZIP+4
• Frequently Asked Questions

What Is ZIP+4?

A ZIP code is the US name for a postal code: a short code for an area that helps the post sort mail. The normal ZIP code has 5 digits. ZIP stands for "Zone Improvement Plan".

ZIP+4 is the long version. It adds 4 more digits to the end of your ZIP code. The USPS calls it the most complete ZIP code. It started in 1983.

Forms and websites use different names for the same thing. Here is what they mean:

Write a ZIP+4 code as 5 digits, a hyphen, and 4 digits. The USPS says the hyphen is required. In fact, it is the one punctuation mark the USPS asks you to keep in an address. You can leave out commas and periods, but not this hyphen.

Sources: USPS Domestic Mail Manual 602, sections 1.8.1 and 1.8.2, USPS: Decoding the ZIP Code, USPS FAQ: ZIP Code The Basics and USPS Publication 28: Punctuation.

What Do the Extra 4 Digits Mean?

Each part of a ZIP+4 code makes the area smaller. Think of boxes inside boxes: a big box for a part of the country, then smaller and smaller boxes, down to a few houses.

Let's take apart 22162-1010. It comes from an example address in the Universal Postal Union's guide to US addresses. The Universal Postal Union is the UN agency for post.

The first 5 digits find the post office. The last 4 find a few streets, then one street side or building.

Read it from left to right. The first 5 digits bring a letter to the right post office. The 4 extra digits tell the post where to go next, inside that post office's area.

How small is a segment? According to the USPS, the last 4 digits together can point to:

• one side of a street, between two crossings
• both sides of a street, between two crossings
• one building
• one floor, or a few floors, of a building
• one company in a building
• a group of mailboxes on a rural route
• a group of PO boxes

One ZIP+4 code can cover a whole street side or just one floor.

This is why your neighbors across the street can have a different +4 than you. A big office building can even have its own +4, and each floor can have another one.

Are There Even More Digits?

Yes. In 1991, the USPS added 2 more digits that point to one home or business. You never write them in an address. They are part of the barcode on many envelopes, which sorting machines read.

Sources: USPS: Decoding the ZIP Code and USPS Domestic Mail Manual 602, sections 1.8.2 and 1.8.3.

Do You Need the Extra 4 Digits?

For most things, no. A letter, a parcel or an online order with the right 5-digit ZIP code gets delivered. Most forms only ask for the 5 digits.

The extra 4 digits matter in a few cases:

• A form asks for them. Some forms have a field for a "9-digit ZIP code" or "ZIP+4", or a small extra box for the 4 digits.
• Businesses that send a lot of mail. The full ZIP+4 helps the post sort their mail by machine.
• You want your address to be complete. The USPS calls ZIP+4 the most complete ZIP code.

If you write the extra digits, write them right. The USPS says a ZIP+4 must be 5 digits, a hyphen, and 4 digits. Mail with a wrong code may move slower or come back to the sender.

Not sure about the 4 digits? Then leave them out. A correct 5-digit ZIP code is better than a guessed 9-digit one.

Sources: USPS FAQ: ZIP Code The Basics and USPS Domestic Mail Manual 602.

How to Find Your Full ZIP Code

There are three easy ways. Only the USPS gives you the official 4 extra digits.

Search your address in the USPS ZIP Code Lookup, then write all 9 digits with a hyphen.

1. Look at your mail. Letters from banks, phone companies or energy companies often show the full ZIP code in your address. Look for 9 digits with a hyphen.
2. Use the USPS ZIP Code Lookup. Open the USPS ZIP Code Lookup and choose the search by address. Type your street address, city and state. The result shows your ZIP code with the 4 extra digits, like 22162-1010.
3. Not sure about your 5-digit ZIP code? Open ZIP Code Lookup. Type your address, or click your home on the map. The tool shows your 5-digit ZIP code, your city, county and state, and the ZIP code area on the map. It is free, and you do not need an account.

ZIP Code Lookup shows the 5-digit ZIP code, not the 4 extra digits. It uses open postal and map data, not the official USPS records. So use it to find and check your ZIP code and see its area. Then get the 4 extra digits from the USPS.

Do you have a long list of addresses or ZIP codes? Bulk ZIP Code Lookup checks the whole file at once. You can paste ZIP+4 codes too, but the result may show only the 5-digit ZIP code area.

Where the ZIP code goes in an address, after the city and the state, is part of the US address format. Our guide to address formatting shows full examples.

Common Mistakes With ZIP+4

Most ZIP+4 mistakes are small, but a form can reject the code, or a letter can take longer. Here is what to check.

• No hyphen, or a space instead. Write 22162-1010, not 221621010 or 22162 1010.
• A neighbor's or friend's +4. The extra digits can be different even on the same street. Look up your own address.
• Guessed digits. Do not make up the last 4 digits. Leave them out, and the 5-digit ZIP code still works.
• An old code after a move. Your +4 belongs to your address, not to you. The USPS also sometimes adds new ZIP codes or changes their areas. Look the code up again after you move.
• A lost zero at the start. Many ZIP codes in the east start with 0. Spreadsheet programs often drop it, so 02108 becomes 2108. Format the column as text before you type or paste the codes.

Sources: USPS FAQ: ZIP Code The Basics and USPS: Decoding the ZIP Code.

Frequently Asked Questions